This is a gcc internal error, probably gcc13 related, I will try to get the details and switch the bug to gcc.

Thanks Dan much appreciated!

(gdb) run
Starting program: /usr/bin/g++ -DHAVE_KIO -DKCOREADDONS_LIB -DQT_CONCURRENT_LIB -DQT_CORE_LIB -DQT_DBUS_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_NO_DEBUG -DQT_NO_FOREACH -DQT_NO_KEYWORDS -DQT_QMLMODELS_LIB -DQT_QML_LIB -DQT_QUICKCONTROLS2_LIB -DQT_QUICK_LIB -DQT_WEBSOCKETS_LIB -DQT_WIDGETS_LIB -DQT_XML_LIB -D_GNU_SOURCE -D_LARGEFILE64_SOURCE -I/home/sharkcz/tokodon/tokodon-23.02.0/redhat-linux-build/src -I/home/sharkcz/tokodon/tokodon-23.02.0/src -I/home/sharkcz/tokodon/tokodon-23.02.0/redhat-linux-build/src/tokodon_static_autogen/include -isystem /usr/include/qt5 -isystem /usr/include/qt5/QtQuick -isystem /usr/include/qt5/QtQmlModels -isystem /usr/include/qt5/QtQml -isystem /usr/include/qt5/QtNetwork -isystem /usr/include/qt5/QtCore -isystem /usr/lib64/qt5/mkspecs/linux-g++ -isystem /usr/include/qt5/QtGui -isystem /usr/include/qt5/QtWebSockets -isystem /usr/include/qt5/QtQuickControls2 -isystem /usr/include/KF5/KI18n -isystem /usr/include/KF5 -isystem /usr/include/KF5/Kirigami2 -isystem /usr/include/KF5/KNotifications -isystem /usr/include/qt5/QtWidgets -isystem /usr/include/qt5/QtDBus -isystem /usr/include/KF5/KConfig -isystem /usr/include/KF5/KConfigCore -isystem /usr/include/KF5/KConfigGui -isystem /usr/include/qt5/QtXml -isystem /usr/include/KF5/KCoreAddons -isystem /usr/include/KF5/KIOWidgets -isystem /usr/include/KF5/KIOGui -isystem /usr/include/KF5/KIOCore -isystem /usr/include/KF5/KIO -isystem /usr/include/KF5/KService -isystem /usr/include/qt5/QtConcurrent -isystem /usr/include/KF5/KWindowSystem -isystem /usr/include/KF5/KJobWidgets -isystem /usr/include/KF5/Solid -isystem /usr/include/KF5/KCompletion -isystem /usr/include/KF5/KWidgetsAddons -isystem /usr/include/KF5/KConfigWidgets -isystem /usr/include/KF5/KCodecs -isystem /usr/include/KF5/KAuthWidgets -isystem /usr/include/KF5/KAuthCore -isystem /usr/include/KF5/KAuth -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mcpu=power8 -mtune=power8 -fasynchronous-unwind-tables -fstack-clash-protection -fno-operator-names -fno-exceptions -Wall -Wextra -Wcast-align -Wchar-subscripts -Wformat-security -Wno-long-long -Wpointer-arith -Wundef -Wnon-virtual-dtor -Woverloaded-virtual -Werror=return-type -Werror=init-self -Wvla -Wdate-time -Wsuggest-override -Wlogical-op -DNDEBUG -std=gnu++17 -fvisibility=hidden -fvisibility-inlines-hidden -fPIC -MD -MT src/CMakeFiles/tokodon_static.dir/linkpaginatedtimelinemodel.cpp.o -MF CMakeFiles/tokodon_static.dir/linkpaginatedtimelinemodel.cpp.o.d -o CMakeFiles/tokodon_static.dir/linkpaginatedtimelinemodel.cpp.o -c /home/sharkcz/tokodon/tokodon-23.02.0/src/linkpaginatedtimelinemodel.cpp
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[Attaching after Thread 0x7ffff7ff34e0 (LWP 18708) vfork to child process 18710]
[New inferior 2 (process 18710)]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[Detaching vfork parent process 18708 after child exec]
[Inferior 1 (process 18708) detached]
process 18710 is executing new program: /usr/libexec/gcc/ppc64le-redhat-linux/13/cc1plus
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Thread 2.1 "cc1plus" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7ff53c0 (LWP 18710)]
process_function_and_variable_attributes (first_var=0x7fffdc638a00, first=0x7fffdc539900) at ../../gcc/cgraphunit.cc:861
Downloading 0.02 MB source file /usr/src/debug/gcc-13.0.1-0.4.fc39.ppc64le/obj-ppc64le-redhat-linux/gcc/../../gcc/cgraphunit.cc
861	      tree decl = node->decl;
(gdb) cont
Continuing.

Thread 2.1 "cc1plus" hit Breakpoint 1, 0x0000000010747e9c in internal_error (gmsgid=0x11927bf8 "%s") at ../../gcc/diagnostic.cc:2138
2138	{
(gdb) bt
#0  0x0000000010747e9c in internal_error (gmsgid=0x11927bf8 "%s") at ../../gcc/diagnostic.cc:2138
#1  0x00000000103f7a5c in crash_signal (signo=11) at ../../gcc/toplev.cc:317
#2  <signal handler called>
#3  process_function_and_variable_attributes (first_var=0x7fffdc638a00, first=0x7fffdc539900) at ../../gcc/cgraphunit.cc:861
#4  analyze_functions (first_time=first_time@entry=true) at ../../gcc/cgraphunit.cc:1181
#5  0x00000000112bf628 in symbol_table::finalize_compilation_unit (this=0x7fffe8080000) at ../../gcc/cgraphunit.cc:2545
#6  0x000000001125c410 in compile_file () at ../../gcc/toplev.cc:474
#7  0x00000000111dd510 in do_compile (no_backend=<optimized out>) at ../../gcc/toplev.cc:2128
#8  toplev::main (this=this@entry=0x7fffffffca00, argc=<optimized out>, argv=<optimized out>) at ../../gcc/toplev.cc:2282
#9  0x00000000111dc5d0 in main (argc=<optimized out>, argv=<optimized out>) at ../../gcc/main.cc:39

Created attachment 1945415 [details]
preprocessed sources

reduced g++ command line with only defines or include paths still reproducing the issue is

/usr/bin/g++ -DHAVE_KIO -DKCOREADDONS_LIB -DQT_CONCURRENT_LIB -DQT_CORE_LIB -DQT_DBUS_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_NO_DEBUG -DQT_NO_FOREACH -DQT_NO_KEYWORDS -DQT_QMLMODELS_LIB -DQT_QML_LIB -DQT_QUICKCONTROLS2_LIB -DQT_QUICK_LIB -DQT_WEBSOCKETS_LIB -DQT_WIDGETS_LIB -DQT_XML_LIB -D_GNU_SOURCE -D_LARGEFILE64_SOURCE -I/home/sharkcz/tokodon/tokodon-23.02.0/redhat-linux-build/src -I/home/sharkcz/tokodon/tokodon-23.02.0/src -I/home/sharkcz/tokodon/tokodon-23.02.0/redhat-linux-build/src/tokodon_static_autogen/include -isystem /usr/include/qt5 -isystem /usr/include/qt5/QtQuick -isystem /usr/include/qt5/QtQmlModels -isystem /usr/include/qt5/QtQml -isystem /usr/include/qt5/QtNetwork -isystem /usr/include/qt5/QtCore -isystem /usr/lib64/qt5/mkspecs/linux-g++ -isystem /usr/include/qt5/QtGui -isystem /usr/include/qt5/QtWebSockets -isystem /usr/include/qt5/QtQuickControls2 -isystem /usr/include/KF5/KI18n -isystem /usr/include/KF5 -isystem /usr/include/KF5/Kirigami2 -isystem /usr/include/KF5/KNotifications -isystem /usr/include/qt5/QtWidgets -isystem /usr/include/qt5/QtDBus -isystem /usr/include/KF5/KConfig -isystem /usr/include/KF5/KConfigCore -isystem /usr/include/KF5/KConfigGui -isystem /usr/include/qt5/QtXml -isystem /usr/include/KF5/KCoreAddons -isystem /usr/include/KF5/KIOWidgets -isystem /usr/include/KF5/KIOGui -isystem /usr/include/KF5/KIOCore -isystem /usr/include/KF5/KIO -isystem /usr/include/KF5/KService -isystem /usr/include/qt5/QtConcurrent -isystem /usr/include/KF5/KWindowSystem -isystem /usr/include/KF5/KJobWidgets -isystem /usr/include/KF5/Solid -isystem /usr/include/KF5/KCompletion -isystem /usr/include/KF5/KWidgetsAddons -isystem /usr/include/KF5/KConfigWidgets -isystem /usr/include/KF5/KCodecs -isystem /usr/include/KF5/KAuthWidgets -isystem /usr/include/KF5/KAuthCore -isystem /usr/include/KF5/KAuth -O2 -pipe -m64 -mcpu=power8 -mtune=power8 -fPIC -o CMakeFiles/tokodon_static.dir/linkpaginatedtimelinemodel.cpp.o -c /home/sharkcz/tokodon/tokodon-23.02.0/src/linkpaginatedtimelinemodel.cpp

cvise reduced to -std=gnu++17 -O2 -mcpu=power8:

template <int __v> struct integral_constant {
  static constexpr int value = __v;
};
using false_type = integral_constant<false>;
template <bool, bool, typename...> struct __result_of_impl;
template <typename _Functor, typename... _ArgTypes>
struct __result_of_impl<false, false, _Functor, _ArgTypes...> {
  typedef decltype(0) type;
};
template <typename... _ArgTypes>
struct __invoke_result
    : __result_of_impl<false_type::value, false_type::value, _ArgTypes...> {};
template <typename, typename _Fn, typename... _Args>
void __invoke_impl(_Fn __f, _Args... __args) {
  __f(__args...);
}
template <typename, typename _Callable, typename... _Args>
void __invoke_r(_Callable __fn, _Args... __args) {
  using __result = __invoke_result<_Args...>;
  using __type = typename __result::type;
  __invoke_impl<__type>(__fn, __args...);
}
struct QString {
  QString(const char *);
};
template <typename> class function;
template <typename _Functor> struct _Base_manager {
  static _Functor _M_get_pointer(int) { __builtin_abort (); }
};
template <typename, typename> class _Function_handler;
template <typename _Res, typename _Functor, typename... _ArgTypes>
struct _Function_handler<_Res(_ArgTypes...), _Functor> {
  using _Base = _Base_manager<_Functor>;
  static _Res _M_invoke(const int &__functor, _ArgTypes &&...__args) {
    auto __trans_tmp_1 = _Base::_M_get_pointer(__functor);
    __invoke_r<_Res>(__trans_tmp_1, __args...);
  }
};
template <typename _Res, typename... _ArgTypes>
struct function<_Res(_ArgTypes...)> {
  template <typename _Functor>
  using _Handler = _Function_handler<_Res(_ArgTypes...), _Functor>;
  template <typename _Functor> function(_Functor) {
    using _My_handler = _Handler<_Functor>;
    _M_invoker = _My_handler::_M_invoke;
  }
  using _Invoker_type = _Res (*)(const int &, _ArgTypes &&...);
  _Invoker_type _M_invoker;
};
struct QRegularExpression {
  QRegularExpression(QString);
};
struct AbstractAccount {
  void get(function<void(AbstractAccount *)>,
           function<void(AbstractAccount *)>);
};
struct AbstractTimelineModel {
  AbstractAccount m_account;
};
struct LinkPaginationTimelineModel : AbstractTimelineModel {
  void fillTimeline();
};
void LinkPaginationTimelineModel::fillTimeline() {
  [] {};
  m_account.get([](AbstractAccount *) { static QRegularExpression re(""); },
                [](AbstractAccount *) {});
}

But, strangely can't reproduce with a cross-compiler from x86_64 to powerpc64le.

This bug appears to have been reported against 'rawhide' during the Fedora Linux 39 development cycle.
Changing version to 39.