Just an addition to point 1: There's also Xournal++ [0]; some parts are based on Xournal but it provides some additional functionality [1].

I switched from Xournal to Xournal++ four weeks ago and it's been a blessing.

[0] https://github.com/xournalpp/xournalpp

[1] https://github.com/xournalpp/xournalpp#features