[Ghoelian]

Organic Maps has a flatpak, though oddly they don't refer to a desktop app on their website anywhere so idk how trustworthy this is.

Unfortunately CoMaps doesn't seem to have desktop client builds at all yet.

[Vinnl]

They do mention it at the bottom: https://organicmaps.app/#community

But it's less full-featured than the mobile-only versions.