I was able to install and (surprisingly) activate TT Premier 2020 on new Mac, but when opening my old return it failed because the state program needed to be installed, and the page for that failed to install my state. Based on other comments on this topic, TT only "supports" the current version (2024) and 3 prior versions (2021-3). Seems if you keep your computer alive then whatever version is working on it will keep working, but if you have to install on a new computer they don't allow new activation at that point.
