Given the magnitude of “science” today, I’m not sure there’s much that can be done in free time. Perhaps a math savant can help out with theoretical difficulties, and amateur astronomers have always played a role in seeing “interesting things”. Perhaps people can participate in clinical trials, but such participation has a huge random component - gotta have the right profile and symptoms for anything but safety trials. However, women and children are often underrepresented so their participation (where ethical) would help.

The largest contribution would be providing programming expertise as those doing science aren’t usually strong in that area. Making Linux and its tools more robust. Improving math and other libraries. Improving networking and data sharing. Even helping research groups develop more robust and reproducible code. The HN community, I assume, is skilled in all aspects of computerization it should be quite useful pushing science forward. If individuals are so furtunate, they can contribute money as well as (or rather than) effort.

Search "citizen science" and you will find plenty of projects where people are contributing in various ways such as contributing spare compute cycles from their home computer for some group computational project, etc.

If you are interested in nature, birds, snakes, trees, flowers, etc. there are often apps and communities for identifying and tracking those things. There are also often census type things for counting trees or birds in your area that directly go towards statistics used by scientists.