My Firefox installation constantly stutters at consistent but ultimately apparently random intervals. I recorded https://profiler.firefox.com/from-browser/calltree/?globalTrackOrder=x8x90wx7&hiddenGlobalTracks=1wx3x5x7&hiddenLocalTracksByPid=25362-0wl~25582-01~27158-0~25985-0~25598-0~18425-0~14941-0~25578-0~27517-0~26777-0~16669-0~25668-0w2~25586-0~26006-01~25884-0~25732-0~27544-0~7098-0~25612-0~25767-01~15136-01~14802-01~25795-0w3~25630-0w3~25574-0wd&thread=yh&v=10 whilst quickly switching between tabs, because that usually induces it.
about:processes displays 100% extension usage at these times, but I don’t know how to ascertain which extension, because it doesn’t provide a process tree. https://download.opensuse.org/repositories/openSUSE:/Factory/standard/x86_64/plasma6-systemmonitor-6.0.2-1.1.x86_64.rpm displays the same — merely “WebExtensions” without any child processes.
I’m not using https://download.mozilla.org/?product=firefox-nightly-latest-l10n-ssl&os=linux64&lang=en-GB, as #nightly would indicate (there’s merely no #Firefox category, and the category is mandatory). I’m using https://download.opensuse.org/repositories/openSUSE:/Factory/standard/x86_64/MozillaFirefox-123.0.1-1.1.x86_64.rpm (on cpe:/o:opensuse:tumbleweed:20240315).