How to exclude everything except a few file extensions?

Good day.

How to exclude everything except a few file extensions?

You could use a regex include… maybe something like this:

--include=[.*\.(txt|zip)$]

This would cause only *.txt and *.zip files to be backed up. (I believe - I haven’t tested it!)

To build on that thought, creating a new backup job eventually (on screen 3) talks about how to set filters. Filters talks about the underlying syntax that the somewhat confusing and sometimes confused GUI tries building for you. Using the three-dot menu to verify what it built is right per filter syntax may be worthwhile.