I came across some user reports regarding Arch Linux [1], in which people describe experiences very similar to my own. It is said that using Firefox Beta resolves the issues.
I am also able to share my screen using Firefox Beta again. However, the line 'loop->recurse > 0' failed at ../src/pipewire/thread-loop.c:425 pw_thread_loop_wait() still appears when using Firefox Beta. I am not sure if this line indicates a bug anyway, but it does not seem to be the only cause. 1: https://bbs.archlinux.org/viewtopic.php?id=305299