

Depends on your interests:
As far as some sort of one-on-one support service, I’m not too sure of online services for that (beyond helping out in specific forums when people ask questions).
You can help out with a variety of different research projects over on the Zooniverse:
https://www.zooniverse.org/
You can help by contributing to the map around your area: https://www.openstreetmap.org/
Help out with research on wildlife in your area:
https://www.inaturalist.org/
Contribute to Wikipedia:
https://www.wikipedia.org/
If you feel passionate about consumer rights, you can contribute to the wiki here:
https://consumerrights.wiki/w/Main_Page
If you like to tinker with electronics, check out Fulu Bounties and get paid for helping to get around DRM on refrigerators or on an Xbox. This has the potential to help a lot of end users as well as prevent E-waste. https://bounties.fulu.org/

I’m honestly surprised by your comment. Is this based on one specific experience you had with someone?
I have also lived there, but I never met any member of that faith who would be offended by being called a Christian. It has always been the opposite experience for me.