Just because the questions haven't been closed doesn't mean they're on topic. The specific policy is:
Any non-official variant or flavor of Ubuntu such as Regolith, Mint, PopOS, etc. are considered offtopic here on Ask Ubuntu.
To quote the Help Center (links stripped by me)
Questions that you may ask:
Using and administering official Ubuntu flavors: Ubuntu, Ubuntu
Budgie, Ubuntu MATE, Kubuntu, Ubuntu Kylin, Lubuntu, Ubuntu Studio and
Running third-party applications on Ubuntu.
Development on Ubuntu.
Services provided by Ubuntu and Canonical.
Any questions not mentioned below or here are great!
Questions that you should avoid:
Linux Mint, Elementary OS, Backtrack, Gnome-Remix (prior to 13.04),
budgie-remix (16.04 and 16.10) and other Linux distributions (try our
friends at Unix & Linux Stack Exchange).
Issues with the next version of Ubuntu (Ubuntu+1)
Shopping or Hardware Recommendations
Support for versions for Ubuntu releases past their Support or "End
of Life" (EOL) — unless the question is asking how to upgrade to a
We could probably expand the first bullet-point of Questions that you should avoid to read as "any non-official flavor or variant of Ubuntu" with a link to the official list of Ubuntu Flavors that are recognized, however this should already be self-explanatory as "Regolith Linux" markets itself as a different non-Ubuntu name, so like Kali or Mint or PopOS, fit into the "other Linux distributions" category.
If you are asking "How do i install the Regolith desktop into my Ubuntu 20.04" system, that could be ontopic, but there's still a chance you'll not be able to get much support since it was designed for Regolith Linux, not Ubuntu itself.