On my Ubuntu 22 based laptop, I can bypass the gnomish (and
characteristically LCD targeted) MouseKeys and instead do it the xkb
way:

    xkbset m ma 160 40 30 30 500

and possibly tweak the parameters to perfection.

But on Debian bullseye with Gnome (and I assume likewise on chimaera)
when I try this I get a message like

    XKB not supported by display :0

I think Debian mostly lets Gnome keep the default configuration?
Anyway why this difference? Maybe something related to Wayland?
Can I get the old flexible MouseKeys on Debian & Devuan too?

--
Ian