Firefox has long been the default web browser for many popular distributions such as Ubuntu and Manjaro. It is well known for its privacy features, as well as being completely open source. It has had many notable UI redesigns over the years, of which the latest was the Photon design.
By coincidence (?) my Mozilla Thunderbird updated from the 68.x series to 78.8.1 this morning. This is on Ubuntu-based Zorin OS Lite. I haven't seen any reports in tech news regarding this being pushed out. The 78.x series has been out for a good while, with some major changes that may break your add-ons. I only use one add-on (manually sort folders) and it seems okay.
EDIT: I neglected to say that this Zorin Lite has not got the new Firefox yet. Still 88.0.1.
None of my buntu base distros have received the Firefox 89 update however Ubuntu has always been a few days behind the Firefox update so it should be coming about shortly.
Ubuntu also includes a wide variety of software through its network of software repositories. Once your system is installed you can simply call up a list of all the existing tools out there and choose any of them for immediate installation over the internet.