I don't know the answer for this but when I used Obsidian with the vault with Nextcloud, I made a huge mess of things. You can use the markdown/.md files (of many markdown editors like I do) in Nextcloud and use it between PCs and phones. I found Syncthing much harder to do this way, so only use Syncthing for my 50GB Music folder and for sharing PC-related things between computers such as themes, icon pack themes, wallpapers, and small programs and .iso files. And, Syncthing is no longer on Android anyway - which is good because I could never get it to work well on Android.
Syncthing
Syncthing is a continuous file synchronization program. It synchronizes files between two or more computers in real time, safely protected from prying eyes.
Your data is your data alone and you deserve to choose where it is stored, whether it is shared with some third party, and how it's transmitted over the internet.
Visit https://syncthing.net/ for more information, downloads and donations
Thanks. It's been some time since my post. I've been able to set up Syncthing, which works great for me. Nextcloud requires a server which is really hard to setup correctly, so I'm settling on Syncthing for now
And, Syncthing is no longer on Android anyway - which is good because I could never get it to work well on Android.
https://github.com/Catfriend1/syncthing-android
I've been using Syncthing-Fork which works great.