.XCompose ibus support in Flatpak apps in Arch Linux

Hello all. Apologies if this has been asked before, but search didn’t yield anything.

I dual boot Pop OS and Arch on my machine, and am trying to migrate as much software to flatpak as possible.

I also require an .XCompose in my home folder with custom key bindings I use to support multi-language input without switching layouts. It works flawlessly with ibus in every distro I’ve ever used.

It so happens that the flatpaks I install via flathub on Pop Os respect my .XCompose file, while the ones I install in Arch don’t. Installation in Arch is done with the --user flag.

The exception in Arch is WPS Office, which respects my .XCompose, but other apps that use the same runtime (like Discord) or any other apps don’t.

Have tested with multiple apps, using different runtimes, and (except for WPS) the result is always the same. .XCompose bindings get passed on in Pop Os, but not in Arch.

Both distros are running GNOME 3.36.2 as the default (and only) DE. All other apps (running outside flatpaks) respect the .XCompose file normally with the appropriate IM_MODULE entries for QT and GTK in the profile file.

Could anyone enlighten me as to what is Pop OS is doing that Arch isn’t that’s causing my .XCompose to be respected?

Thanks in advance.