Tor Project recently received funding to factor out the security and privacy enhancements of Tor Browser from the Tor-specific enhancements (similar to how Kicksecure factors out security features from Whonix). The factored-out browser is called Base Browser . This is basically the same concept as SecBrowser, which was deprecated by Kicksecure due to insufficient support from upstream Tor Project. There aren’t yet any Nightly builds of Base Browser, but code is already being committed to Git; I’m not sure what the expected release timeline is.
It might be useful for Kicksecure to consider including Base Browser once it’s released (at least as Nightly). I’m guessing the Tor Browser Downloader in Whonix could be trivially adapted for Base Browser.
 I was initially not very fond of this name, but it’s grown on me, especially once I realized that it opens the door to entertaining memes such as “In Soviet Russia, all your tracker are belong to Base Browser.”
My recollection was that there were severe UX issues with SecBrowser that were primarily caused by the Tor Browser codebase not being compatible with the changes SecBrowser wanted to make, e.g. the window title saying “Tor Browser” still, and that this was why it was deprecated? If that’s correct, I would say the root cause of the deprecation was insufficient support from upstream. Anyway I’ll defer to you on this since you obviously know the history better than I do, so apologies if I misstated the reasons.
Now that the big announcement was made this morning, I can disclose who funded Base Browser. Mullvad contracted Tor Project to make Mullvad Browser, which (like Tor Browser) is a derivative of Base Browser.