Mullvad Browser's download page for macos [1] says that it works on macos Big Sur (11) or later. So the first time I saw that just after the announcement, I did not download it since I use an older macos as my daily driver (I know version is not supported by Apple anymore).
Today I downloaded Mullvad Browser anyway, and tried it on my pre-11 macos. It works just fine. So I thought of letting others know, just in case it helps. Plus, Mullvad may want to test it on older OS and update the download page to clarify support for older OS versions.
[1]: https://mullvad.net/en/download/browser/macos