LULU just Stopped being compatible with my old iMac running High Sierra. What are the alternatives?

I've loved using Lulu for years to block outgoing connections but all of a sudden it's disappeared from my system and I get a popup saying the newer version is no longer compatible with my version of High Sierra.

Can't find older versions that would be compatible so I'm feeling confused. If I can't get an older version to work on my High Sierra v.10.13.6 , what are my alternatives?

Any help is greatly appreciated. Thanks a bunch!