Key features:
- PDF annotation
- S-pen/stylus support
- Sync (preferably NOT just via Nextcloud…looking at you, Saber)
- Handwriting recognition is a plus, but not required
As mention above, Saber fits the criteria well, but I don't use Nextcloud and that is the only sync available in that app (unless something has changed in the last couple of weeks). I have a Galaxy phone and tablet that both support S-pen and Samsung Notes is excellent, and free, but they're not exactly privacy concious, so I'm looking elsewhere. I had considered the Excalidraw plugin for Obsidian, but I'm not sure if that works on the Android version of the app.
Fair point, do you have any in mind?
My Note 4 died last year so I don't have any android suggestions, sorry. On Linux I like Rnote, but it's fairly early in development and I last time I wanted to annotate a PDF I had to do so in Xournal++
Orgmode?
It can do S-pen notes?
Oops. Missed that. My bad