On desktop: Nvim with some markdown plugins plus Goyo
On mobile: Obsidian
Syncthing for sync (though previously I've Dropbox as well for the same)
On desktop I find Obsidian's vim mode slightly uncanny valley-ish. Close enough to be able to emulate my vim flow. But not _quite_ right.
On mobile, I've found Obsidian to be just top class. Though admittedly most of my real note taking happens on desktop, on the few occassions I've had to jot down something quick on mobile, Obsidian app has been perfect.