profiler VS xkeysnail

Probably your best bet is to use the Firefox Profiler once it starts hogging the CPU to try to see what it's doing. I'd be happy to take a look at the result although I don't have a lot of experience at diagnosing performance problems; hopefully the profile will make it obvious what's going on.

I tried using the https://profiler.firefox.com/ and running with:

You can try to reproduce while taking a profile using the Firefox profiler, then share it in the #perf:mozilla.org room on Mozilla's Matrix instance.

Run a profiling session for ~30 sec when you notice something is running slower than you expect, see https://profiler.firefox.com/. Share results here if you want help interpreting them.

Next time, send a SIGABRT to the main process (kill -6 $(pidof firefox)) and use the resulting backtrace (you will find a link to the crash report in about:crashes) to file a bug. A performance profile could be useful, but you'll need to know first what to capture. This seems like a graphics issue, so try the Graphics preset. Share a link to your report.

https://profiler.firefox.com will be useful if you can capture and share it to developers.

If you can reproduce it in safe mode and a clean profile, capture a performance profile using the clean profile while trying to load a problematic webpage, don't remove any information from it, and share it here (although it's typically not easy for users to analyse them), or file a bug with it attached.

Next time, capture a performance profile using the Graphics preset, and kill the browser by entering kill -6 $(pidof firefox) in a shell. This will create a bug report (unless debian disables the crash reporter) that would indicate where Firefox is stuck at. You might need to use an official build to get useful results.

FYI: You can enable them in Gnome with Gnome-Tweaks. Apparently a very recent version of Gnome dropped this functionality for reasons that are beyond my understanding (but that's often the case when I look at the decisions that the Gnome devs make).

However, getting the Control -> Command/Super thing to work is much trickier. The best way is to use this: https://github.com/mooz/xkeysnail

However when I tried that, I ran into all kinds of weird behaviours all over the OS. Also, it doesn't work with Wayland.

If the likes of https://github.com/mooz/xkeysnail/issues/43 are still a going concern then it's not quite as "everywhere" as one would like, and I presume that issue is a fundamental one (i.e. it doesn't sound like XKeySnail gets first refusal on key events).

And I use XKeySnail to have the basic Emacs keys everywhere. I'm sure there are others, but it does enough to keep me happy.

https://github.com/mooz/xkeysnail or the fork of it, I forget it's name, will allow you to do the same as exwm's simulation keys with any window manager.

Thanks for the suggestion guys. I decided to go with xkeysnail ( https://github.com/mooz/xkeysnail/ ). So far so good.

Similar options for Linux users are keyd and xkeysnail

https://github.com/mooz/xkeysnail or something similar ?

Bind everything you want: https://github.com/mooz/xkeysnail

xkeysnail is not bad in the two sense, however, there are some application do can distinguish them, say, chrome and neovide

If you're using x11, there's xkeysnail