You don't have to manually sync, the phone app has a Dropbox/SyncThing/whatever integration so everything's synced automatically. On desktop, it's a file that you sync via Dropbox/SyncThing/whatever. Harder than a third party app, but if you're comfortable syncing files, then you can very comfortably use an offline password manager (I have for 10 years on my phone and the UX is basically the exact same as using my work appointed password manager).