Comment 0 for bug 2000839

Firefox 110+ requires rustc 1.65 and cargo 0.66 to build¹.

The beta phase for Firefox 110.0 begins on 2023-01-16 and release candidates will be available from 2022-02-06.

We will need these in Ubuntu 23.04 and all supported releases: bionic, focal, jammy, kinetic.

¹ https://bugzilla.mozilla.org/show_bug.cgi?id=1807761

Rust toolchain upgrades are usually relatively safe from a FTBFS point of view, since new releases are subjected to a crater run, crater being a tool that compiles the entirety of the crates.io packages.