It’s been asked many times over the years but I can’t be arsed to do a forum search…
I’m trying to troubleshoot clicking on a SketchUp file and having it open with 2023, so I want to uninstall all my SketchUp versions and then re-install 2023 back first, and then I want to re-install my classic license 2021.
Do I need to deauthorise 2021 on my machine and if so how?
For the license part, only the latest Classic version of a license that you have activated, can be activated on a future new machine. So, you may as well not remove any licenses on this machine. 2021 will rediscover its 2021 license when you reinstall 2021. If at some point you have to do something that only works in 2019, for example, you could install 2019 on this machine, and it would find its old license.
And yes, to reinstall 2021 you would need to uninstall 2022 and/or 2023.