I’m running into this same problem. Can’t deserialize HashSets anymore.
It’s super frustrating because Unity 2021.3 is supposed to be LTS but between 2021.3.1f1 and 2021.3.2f1 a breaking change was made where looking in the package dependencies, the package “com.unity.services.core” now directly depends on “com.unity.nuget.newtonsoft-json”.
I was using my own copy of newtonsoft json in my Assets folder, but because of Unity now requiring use of the nuget package, I had to delete my own copy in my Assets folder to fix the duplicate symbol errors.
Then my game crashes for some reason and I’ve tracked it down to not being able to deserialize HashSets from the game saves.
I’ve wasted a full day trying to fix this issue … just from upgrading a point version from 2021.3.1f1 to 2021.3.2f1 … dealing with stuff like this makes me want to pull my hair out! Why does Unity keep making breaking changes between point versions wasting our time so much?
Tried doing this, but still got errors at runtime:
Gonna have to call it a day.