Yup, so we just don't know, we know that most pathfinder 2e players aren't using roll 20, but not their size on the platform they are using (or what percentage of players of other systems are using Foundry)
Is there a reason why Roll20 is worse for PF2e than for 1e? My expectation would have been that Roll20 support would correlate with popularity both ways - popular games get more support, and support affects popularity.
Edit: Checking the Roll20 marketplace I thought the support for both PF1e & 2e looked pretty sketchy, with only a few APs, some abandoned half-finished, and such. Price also seemed offputting, with a single book of a PF AP comparable to the cheaper WoTC 5e campaign books. So only Rise of the Runelords really looked like a good deal for most people.