Firefox’s free VPN will offer 50 gigabytes of monthly data, which is pretty generous for a browser-based VPN. A Mozilla account is required to make use of it, which isn’t a hardship (they’re free), but is a point of friction some may wish to know upfront.
The same could be said about any VPN out there. Read the ToS and privacy policy, and either believe it or don’t.
True, but Mozilla being what it had been the past few years I trust them no further than I can throw them
Edit: pay the few dollars for mullvad