We don't make choices on that since it requires an extremely high degree of trust to use a VPN. I am aware IVPN, Proton VPN and Mullvad have exceptional reputation but that isn't a formal recommendation. Some members go beyond and use Tor. For someone around Nostr I heard IVPN accepts Lightning and Mullvad has lightning resellers so that would likely be better for them.

I just use what I like. There's a lot of things people would enjoy knowing I use, but I also use a lot of things people in a lot of spaces would lynch me for using as well. Use what is best for you and learn more about that choice to help establish trust beforehand.