I’ll second this one. I love Proton. It’s the only free service, other than the late Apollo, that I’ve ever decided to pay to upgrade just because I love it so much. It also happens to be well worth paying for imo.

As with any service, unless you build and host it all yourself, you’re ultimately trusting some one else with your data. However, Proton are generally very transparent and, as you say, seem to really know their shit. For those reasons I choose to trust their services.