BOINC is still probably the gold standard for distributed compute. You ca n choose multiple projects to contribute to based on what you’d like to support (mathematics, astronomy, medical/biology, etc)

That said, consider that power on loaded time does add gradual wear to electronic components.
I used to run multiple crunching machines pre 2020, but I admit In the current market I mothballed them all both for power cost and for long term stability. I need my current hardware stack to last until 2032 most likely, and I’d rather not be hammering it with a 24/7 load that entire time, because they are basically unreplacable now.