I use Proton’s VPN.
Issues I’ve observed: timeouts and extra (sometimes excessive) “are you human” verifications, extra step on troubleshootings if a site doesn’t load properly or at all, sites load slower, connection may not even work when it’s morning in Russia and China or if the server is in a country being bombarded (e.g. Iran’s former allies) or possibly also going through some natural disaster, some sites may hardcode your VPN region to your account if you stay in a given IP too much (e.g. Crunchyroll), and some sites block VPN IPs they know about (e.g. Nijimiss.moe, part of the fediverse, and GameFAQS).






Going by reports I’d see, people I see banned from Reddit mainly were either promoting alternatives or using VPNs.
And since I experienced my own account being silently banned when I tried to log in, being logged to a VPN at the moment I tried to do it despite never having a problem before, and I hadn’t used it since I learned about ActivityPub so no local comments about the fediverse, seems very likely to be the case.
That, or they’re monitoring people even when the user is away from their platform, which would be creepy at best.