>You could add "I don't care about fixing security vulnerabilities" somewhere in the beginning of the readme

I care about fixing security vulnerabilities in my OS projects, but I care more about my sanity, my family, getting enough money to survive, and a few other things. Unless you pay me I don't care about your problems with my free (as in a beer) software.

And that's a good thing btw - I tried to ask for donations once, got the equivalent of a few cups of coffee per month, and... burned out almost immediately. I started to feel responsible for that project, staying up late to fix reported minor bugs, and it turns out watching Github issues 365 days a year for a few dollars monthly is not a great business strategy.