I've programmed my keyboard (bit round the houses as I can't directly assign copy and paste keycodes) so Fn+X/C/V send XF86Cut/Copy/Paste.
It works in Firefox. Yay!
It doesn't work in anything else I've tried, but according to that article GTK and Qt are being updated and they usually handle copy/paste rather than the apps themselves.
Looking forward to ditching Ctrl+C, which should never have been a copy shortcut in the first place.
I found this handy snippet to enable these keys in GTK 2 and 3 (not sure of the equivalent for GTK 4 but I guess that's the one which has been updated anyway): https://forum.colemak.com/topic/1438-dreymars-big-bag-of-keyboard-tricks-linuxxkb-files-included/#p10012
Unfortunately I've found this whilst I'm not at the right computer so I haven't been able to test them.
Edit: I tested this and it doesn't appear to have helped.