You could try rnote and xournalpp for PDF annotation. It works pretty well in my expeience for handwriting. I’d reccommend rnote over xournalpp since it can directly save to pdf (iirc), and you can also have an infinite canvas, so it would also be a good OneNote replacement in that department. For popup notes, inline text and stuff, okular from KDE works pretty well for me, but I have also heard good things about the GNOME pdf viewer (UI wise). Haven’t used the GNOME pdf viewer though, so can’t attest to features.
You could try rnote and xournalpp for PDF annotation. It works pretty well in my expeience for handwriting. I’d reccommend rnote over xournalpp since it can directly save to pdf (iirc), and you can also have an infinite canvas, so it would also be a good OneNote replacement in that department. For popup notes, inline text and stuff, okular from KDE works pretty well for me, but I have also heard good things about the GNOME pdf viewer (UI wise). Haven’t used the GNOME pdf viewer though, so can’t attest to features.