I make 2 compromises in my open source software work in order to keep up with all the projects I start and at least do a decent job maintaining some of it:

1. I don't support old stuff. No old operating systems, no old dependencies, no old compilers, etc. The answer to all support requests of the sort is "sorry, I don't have the time or funding to support versions below XYZ."

2. I'm not afraid to roll the major version number of my software. If I make a design mistake, I fix it without regard for backward compatibility, and then I don't support older versions.

These two things really make a big difference in lowering the difficulty of support without compromising the quality of at least the latest version of code. And if the users are using the latest version of everything and need support, great! They probably have such a similar environment to my own that I'll have no problem reproducing their issues.