The only stable client ATM is https://app.element.io/ (or any other web installation of Element). FWIW, Element upstream only supports officially packaging .deb for Ubuntu, and all Flatpaks/AppImages I’ve found only unzip that .deb and move stuff into a flatpak structure. None of them builds from sources. That bad practice by itself can probably be a source of these random crashes.
Although none of these are exactly a Fedora problem, the reality is that this makes the chatting/calling experience awful. None of the clients are supported by Fedora, and those that you can get to use always end up crashing. Since Fedora uses Matrix as an official communications channel, one would expect to be able to use it pleasantly out of the box in a Fedora Workstation.
Possible solutions:
Somebody from Fedora, with the required knowledge, could step in and fix those upstream issues.
I also started looking into this a few weeks ago when element’s desktop app started continuously crashing on me and I found the same problems you listed above. The issues with getting an electron app packaged and upstream’s attitude toward the flathub release made me start looking for an alternative.
I’m not sure why nheko never showed up in my earlier searches but I’m going to look at it as well but once fluffychat’s upstream issue is resolved, you should at least have another option.
I use fluffychat on phone, but really for desktop it has a very subpar experience compared with a buggy Element. It seems to target too much for mobile devices. No shortcuts, no threads, flaky search, no (or buggy) videocalls (main problem for me)…