how can re-install the 2018 version

I find it interesting that Adobe won't support there software unless you buy their cloud subscription which I have no interest in. I bought a newer version 2021 and installed it on my main computer where it nags me every time I open it telling me sign in is required which I never do. Luckily I'm able to close out of that screen and use the program. I also have a 2018 version which I removed from my main computer and wanted to install it on a different computer that the serial number can't be validated. I've checked my account and both versions are showing. The serial number for the 2018 version matches what I entered during setup. I'm guessing this is Adobe's way of trying to force people to buy in to their cash cow.