I haven't seen others mention it yet, but for a while I also self-hosted https:/)mailinabox.email/ and used it for what you described.

Nice. I had not seen saber. Just installed it on my laptop and phone, and got it connected to my next cloud instance.

Like others have said Joplin's drawing is terrible, and xournal has been the best so far but is difficult to manage and review as a notebook.

Too bad I can't do a big sweep my xopp file to convert to saber to get a feeling with existing notes. https://github.com/saber-notes/saber/issues/677