I quite like Obsidian too. Markdown note app that has desktop & mobile versions. You can create templates and have it so that a new note using a template is opened automatically when you open the app (e.g. for daily notes). It also supports a lot of different community created plugins.
I sync across android & linux via google drive for free, otherwise Obsidian also has a paid sync feature.
yup, this is what I do and it works great. just be careful if you add plugins that store a ton of metadata that changes a lot (or logs) because that can lead to some sync conflicts and you might wanna exclude them. I've just been ignoring the sync conflicts tho and haven't had issues yet so maybe you could do the same