I made it for android too, I just need to get some testers onboarded:
https://groups.google.com/g/tabletop-jigsaw-testers
37 karma · joined December 14, 2015
The way I use it it's relatively simple, I tend to forget a lot so I leave notes, documentation, references, know hows and pretty much everything I judge that I will need in the future and will definitely forget.
In order to sync it with my other computers, I use another tool (Nextcloud), hosted on my homelab. I know it requires signing in but, think about it, it comes with clients for linux, windows and mac and phone (but I haven't tried zettlr for phone, not even sure they have it). With this you will get the best of both worlds: cloud and local.