It's been a while since I ran a receiver, but back when I did ADSBExchange was pretty popular. It looks like there are a number of other options at the moment though - like ADSB.lol and airplanes.live
That project is now commercial, but it still shows flights and aircraft that many of the other commercial ones do not. I agree though, supporting the non-commercial ones is important too. I should update my own feeder to do more.
And anecdotally they now censor some things, as I'm seeing much less private jet and helicopter activity than I used to, especially those that have to be triangulated.
If you do set this up, consider also feeding data to non-commercial aggregators who make their data available for free and do not censor certain flights: https://github.com/rickstaa/awesome-adsb?tab=readme-ov-file#...
It's been a while since I ran a receiver, but back when I did ADSBExchange was pretty popular. It looks like there are a number of other options at the moment though - like ADSB.lol and airplanes.live