How to use lower version Packages in 2021.2?

In the 2020.2 version, in the package manager, you can choose other versions

 

Simple, if they're not there, it means older package versions aren't supported in the Unity version you're using.

 

You can enter the package name and version. As an example if you wanted Addressables 1.17.17, you could click the +, select "Add package by name", type com.unity.addressables, type 1.17.17 in version box and click Add. However, as mentioned above, the version may not be compatible.

 

In previous versions of the package manager it was possible to choose version from a list, now we have to type the version manually.
Why?
I see in the Unity 2022 beta the package manager has changed its interface again and this time it shows a "versions" tab, but it only lists the current one and the recommended one if it's not already the current one. That's not a useful list of versions. There's no way to upgrade/downgrade versions to test compatibility, and writing versions by hand is not that easy because there's no list of all the versions anywhere, which sometimes include things like -pre or -preview and require knowing the exact number version.


Before:



Now: