Ah, Gnome is currently in a draft process for offline maps.
Taken from a draft open merge request
"Only map viewing works in offline mode"
https://gitlab.gnome.org/GNOME/gnome-maps/-/merge_requests/512
🐧 🐧🐧
I'm unsure what you could try other than give Waydroid a try and run fdroid+comaps within an android container.
This would be tad bit technical to setup, hardware acceleration functions with Intel+AMD GPUs but not Nvidia & kind of cpu intensive way to go about running offline maps.