As usual, the answer to my question lived in a course I bought years ago but hadn't gone through....
Chris Fideo's course on MySQL backups from 2019 has some great info on this, and a strategy that I'll be attempting to put into place over the next few days.
In essence, enabling database binlogs, then setting up a 2nd server to act as a replication database but just grabbing/storing the binlogs.
- Do full database backup periodically using the master_data=2 to store current binlog position
- Store binlogs, and if needed backup from latest backup + binlogs after the position noted in Step 1
Lots of setup required, but that course is the way to go for this... It makes sense that there's no "simple" package that deals with it, given that you've got to update settings & have admin access to the folders to see/grab the binlogs (OR have a separate server & db user set up to grab/store the binlogs).