Further, when trying to build with flann I get these linker errors, so it looks like flann is built without lz4:

[ 60%] Linking CXX executable verdandi
cd /builddir/build/BUILD/hugin-2023.0.0/redhat-linux-build/src/tools && /usr/bin/cmake -E cmake_link_script CMakeFiles/verdandi.dir/link.txt --verbose=1
/usr/bin/g++ -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  -mbranch-protection=standard -fasynchronous-unwind-tables -fstack-clash-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -O2 -g -DNDEBUG -Wl,-z,relro -Wl,--as-needed  -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -Wl,--build-id=sha1 -specs=/usr/lib/rpm/redhat/redhat-package-notes -fopenmp CMakeFiles/verdandi.dir/verdandi.cpp.o -o verdandi  -Wl,-rpath,/builddir/build/BUILD/hugin-2023.0.0/redhat-linux-build/src/hugin_base: ../hugin_base/libhuginbase.so.0.0 /usr/lib64/libpano13.so ../foreign/levmar/libhuginlevmar.a /usr/lib64/libGLEW.so /usr/lib64/libboost_filesystem.so.1.81.0 /usr/lib64/libboost_system.so.1.81.0 /usr/lib64/libfftw3.so /usr/lib64/libvigraimpex.so /usr/lib64/libOpenEXR.so /usr/lib64/libImath-3_1.so /usr/lib64/libIex-3_1.so /usr/lib64/libIlmThread-3_1.so /usr/lib64/libz.so /usr/lib64/libjpeg.so /usr/lib64/libtiff.so /usr/lib64/libpng.so /usr/lib64/libz.so /usr/lib64/libz.so /usr/lib64/libexiv2.so /usr/lib64/liblcms2.so /usr/lib64/libvigraimpex.so /usr/lib64/libOpenEXR.so /usr/lib64/libImath-3_1.so /usr/lib64/libIex-3_1.so /usr/lib64/libIlmThread-3_1.so /usr/lib64/libz.so /usr/lib64/libjpeg.so /usr/lib64/libtiff.so /usr/lib64/libpng.so /usr/lib64/libz.so /usr/lib64/libz.so /usr/lib64/libexiv2.so /usr/lib64/libboost_atomic.so.1.81.0 /usr/lib64/libX11.so /usr/lib64/libpano13.so /usr/lib64/libOpenGL.so /usr/lib64/libGLX.so /usr/lib64/libGLU.so /usr/lib64/libGLEW.so /usr/lib64/libsqlite3.so /usr/lib64/libOpenEXR.so /usr/lib64/libImath-3_1.so /usr/lib64/libIex-3_1.so /usr/lib64/libIlmThread-3_1.so /usr/lib64/libjpeg.so /usr/lib64/libpng.so /usr/lib64/libOpenEXR.so /usr/lib64/libImath-3_1.so /usr/lib64/libIex-3_1.so /usr/lib64/libIlmThread-3_1.so /usr/lib64/libz.so /usr/lib64/libjpeg.so /usr/lib64/libpng.so /usr/lib64/libvigraimpex.so /usr/lib64/libexiv2.so /usr/lib64/libtiff.so /usr/lib64/liblcms2.so 
/usr/bin/ld: /tmp/cckml5Mr.ltrans1.ltrans.o: in function `flann::serialization::SaveArchive::flushBlock()':
/usr/include/flann/util/serialization.h:425: undefined reference to `LZ4_compress_HC_continue'
/usr/bin/ld: /usr/include/flann/util/serialization.h:443: undefined reference to `LZ4_compress_HC_continue'
/usr/bin/ld: /tmp/cckml5Mr.ltrans4.ltrans.o: in function `flann::KMeansIndex<flann::L2<double> >::saveIndex(_IO_FILE*)':
/usr/include/flann/util/serialization.h:406: undefined reference to `LZ4_resetStreamHC'
/usr/bin/ld: /tmp/cckml5Mr.ltrans4.ltrans.o: in function `flann::LinearIndex<flann::L2<double> >::saveIndex(_IO_FILE*)':
/usr/include/flann/util/serialization.h:406: undefined reference to `LZ4_resetStreamHC'
/usr/bin/ld: /tmp/cckml5Mr.ltrans4.ltrans.o: in function `flann::KDTreeIndex<flann::L2<double> >::saveIndex(_IO_FILE*)':
/usr/include/flann/util/serialization.h:406: undefined reference to `LZ4_resetStreamHC'
/usr/bin/ld: /tmp/cckml5Mr.ltrans4.ltrans.o: in function `flann::KDTreeSingleIndex<flann::L2<double> >::saveIndex(_IO_FILE*)':
/usr/include/flann/util/serialization.h:406: undefined reference to `LZ4_resetStreamHC'
/usr/bin/ld: /tmp/cckml5Mr.ltrans3.ltrans.o: in function `flann::LshIndex<flann::L2<double> >::saveIndex(_IO_FILE*)':
/usr/include/flann/util/serialization.h:406: undefined reference to `LZ4_resetStreamHC'
/usr/bin/ld: /tmp/cckml5Mr.ltrans3.ltrans.o:/usr/include/flann/util/serialization.h:406: more undefined references to `LZ4_resetStreamHC' follow

See: https://download.copr.fedorainfracloud.org/results/bpostle/panorama/fedora-39-aarch64/06437242-hugin/builder-live.log.gz

Ignore comment1 above, I probably need to fix this elsewhere. However flann-devel should still require lz4-devel

The second problem appears to be caused by a stray semicolon in the flann.pc file:

    $ pkg-config flann --libs
    -L/usr/lib64\;-llz4 -lflann -lflann_cpp

See also debian bug report: https://bugs.debian.org/1052649

See also upstream bug report:
https://github.com/flann-lib/flann/issues/514

FEDORA-2023-037074502f has been submitted as an update to Fedora 40. https://bodhi.fedoraproject.org/updates/FEDORA-2023-037074502f

FEDORA-2023-037074502f has been pushed to the Fedora 40 stable repository.
If problem still persists, please make note of it in this bug report.

FEDORA-2023-d1b29c8ae9 has been submitted as an update to Fedora 39. https://bodhi.fedoraproject.org/updates/FEDORA-2023-d1b29c8ae9

FEDORA-2023-d1b29c8ae9 has been pushed to the Fedora 39 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2023-d1b29c8ae9`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2023-d1b29c8ae9

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

FEDORA-2023-d1b29c8ae9 has been pushed to the Fedora 39 stable repository.
If problem still persists, please make note of it in this bug report.