I’ve been using my own spamassassin-milter (your third option) with Postfix 3.3.0 for a few months and am happy with it. This project is ‘done’, the initial development phase is through, but it is active.
(I wrote about the why in these places:) https://mail-archives.apache.org/mod_mbox/spamassassin-users/202003.mbox/%3C20200309164349.GA16974%40azadi%3E https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=953018 -- David
