Ok, so this is very early stage but cool:
#Verso is a project to build a full "#FOSS forever" web browser based on #Rust and #Servo rather than #Chromium/#Gecko. Even the interface is rendered with Servo.
https://github.com/versotile-org/verso
Currently there's 23 contributors and a non profit forming to oversee it. There are also nightly releases for testing (remember the "very early stage" bit though!).
Here's their initial launch video (tech starts about 1/2 way through):
https://yewtu.be/watch?v=cqFfpeMGYk4?t=887