Logseq with Syncthing if you want cross device operation.

Yeah, sounds like a permissions error.

Yes, you need to buy (register) a domain beforehand.
The e-mail provider of your choice that provides custom domains will ask you to

• either point your domain to their nameservers (done from the domain provider’s panel)
• or insert/update some DNS records on your domain (either from your domain provider’s panel if it is supported or you can link your domain to another DNS service e.g. CloudFlare)

This might help you: https://iliasa.eu/wireguard-how-to-access-a-peers-local-network/

No problems at all.
I setup a 3-way folder sync between 3 nodes:

1. Desktop (Linux)
2. Android
3. VPS

VPS is always on, so even if my smartphone is not connected to the internet when I log off of my desktop, the smartphone automatically fetches the updated folder from the VPS .

I haven’t used git for this purpose but I’d think the process would be tedious. Manual commit, push, fetch …

Also, I tried to set it up with Nextcloud but I couldn’t get Android Logseq to use the Nextcloud folder for some reason. I don’t remember the exact issue.

That’s what I use.
Logseq with Syncthing for interoperability between my PC & smartphone.