Last I checked, it was working fine in firefox and chrome for my Chromebook, either Kubuntu 23.04 or Neon, or both. I am running Fedora atm, as it has audio support ootb for my specific hardware. Maliit is not working well, if at all, there.
I imagine you may need some extra configuration for this in Arch, making sure it is actually running in Wayland proper, etc.
Before I installed Fcitx5, Maliit worked with Konsole, but not with Firefox; After installing Fcitx, it no longer works, even if I quit Fcitx. (Above was tested after changing the virtual keyboard setting to Maliit and rebooted)