2.1.26 is available - https://changes.ankiweb.net/

This bug appears to have been reported against 'rawhide' during the Fedora 33 development cycle.
Changing version to 33.

According to https://apps.ankiweb.net/ version 2.1.33 is now the latest stable release.

FWIW I had a quick look at recompiling anki and it's become a pretty big monster: some python, rust (python-rust built with maturin), nodejs...

maturin isn't packaged, part of anki also requires orjson as a dependency which only builds with rust nightly, well, honestly at this point I'd just say this isn't going to work.
Looking around all distros imposing stable rust are stuck on 2.1.15 (at least fedora, debian unstable, nixos) and upstream knows about it & advocates using their own binaries from a tar instead of "obsolete versions" in distro packages -- it might be worth just removing it and advising people to use the flatpak instead :|

Please do not remove this outdated Anki version just yet.
The flatpak as all fun and games and sandboxing is awesome, but it does not quite support all features of the native Anki version (yet).
For example, it does not come with a LaTeX environment, so creating cards containing mathematical notation and similar stuff is not possible with the flatpak version, but works great with the outdated 2.1.15.

I looked at anki >= 2.1.17 a while ago (and now again) and I concur: getting it updated in Fedora will be very complicated or probably even impossible. Anki's new build infrastructure relies heavily on downloading the dependencies during the build process via pip, npm and rustup.

Debian: mentions similar problems and hasn't updated anki either:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=958853

ArchLinux: anki is updated, they seem to have more relaxed rules when building packages (allowing to download the dependencies during the build process)
https://github.com/archlinux/svntogit-community/blob/packages/anki/trunk/PKGBUILD

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I would keep it open as a reminder that the problem still exists (2.1.15 in rawhide) - for people looking for a reason.

However, I completely understand Dominique's and Christian's explanations why it is hard and why it probably will not happen for RPM.

Flatmap is some alternative...

I didn't look again recently but according to comments in https://github.com/NixOS/nixpkgs/issues/78449 the orjson problem I pointed to has been resolved (was made optional again in 2.1.41, and now compiles with stable rustc so we could technically even include it)

That leaves maturin and other unpackaged dependencies -- basically going to be a lot of work, but technically possible to package unless it changed, I was able to make a build that doesn't rely on internet for nixos back last year (Oct 2020) and was only stuck for orjson.

I don't have the kind of time to try again now though, so leaving this mountain for a courageous contributor later...

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