The program was recently updated after 6 years.
Not quite sure what was added in the jump to v1 (says "too many to track" in the changelog), but at least the 1.0.1 supports the Logitech Lightspeed receiver which is new and widely used.

Link to tarball: https://github.com/pwr-Solaar/Solaar/archive/1.0.1.tar.gz

Cheers