Since WordPress 5.5, you can easily switch to any other AcyMailing version by installing it over the previous one. You don't need to uninstall the previous version anymore.
Once you've selected the new package, WordPress will ask you if you want to replace the current instance by the one you just uploaded, say yes:
If you have an old version of WordPress and want to keep it that way, you'll need to uninstall the previous version first.
Switching to another AcyMailing edition is easy, just install the new version over the previous one. You don't need to uninstall your previous AcyMailing version.