I never solved this issue. I just tried to solve all merges through the cli on a laptop or desktop. Eventually, I switched to syncthing, and I haven't looked back.

It's not answer you want but I'll say it anyway: I use FolderSync, it works without any problem.

When I started with Obsidian I had the idea that I would use Git to sync between my devices. I ended up just paying for their sync service. There's no good way (that I could find) for cloning a git repo onto an android phone in a way that another app can then use the repo and easily resolve merges.

Syncthing

It's a FOSS, real time, continuous file sync

From personal experience, it works flawlessly between Linux and Android. And it supports Linux, Windows, MacOS, iOS, and Android.

Pairing two devices is seamless, although setting up folder sync can be a bit of a pain

Tip:
If you already have two copies of a folder on separate devices (A and B), you only need to add one copy into syncthing (device A). Then you can share it to the other devices (B), and map it to an [existing or new] folder on B

If you add the folder to A and B separately, then try to share it, you get duplicate "Share" folders, and it gets a bit confusing

The "Folder ID" should be the same across devices