Actually, FLOSS is more precise, given the “L” coming from “libre” in castilian (spanish now a days) referring explicitly to freedom. But it so happen open source != free/libre software, therefore open source usually disregard the philosophic aspect of freedom, which might turn against the users interest, which is what GNU guys were trying to prevent all along, because focusing in the practical aspects, without any concern on the principals behind, actually do have implications on the software itself and its usage.

Yeah, Librewolf by default doesn’t use DoT neither DoH, and so your IP is still exposed, but Librewolf had made it fairly easy to change through preferences or the librewolf overrides, whatever more convenient, as stated on its DoH enabling documentation.

Librewolf is a privacy oriented fork of Firefox, it grabs some setting from arkenfox. Betterbird is not a privacy oriented fork of Thunderbird as far as I remember. When I tried it the only thing I was attracted to was its tray support, but as I use non DE compositors, so far wayfire, labwc and sway (tabbed layout), and as there’s currently a Firefox bug, I didn’t see any reason to keep trying it, and now on sway with tabbed layout I see no reason for a tray any ways…