Question Objects being deserialized is from a more recent version of Unity - Console Error

I recently needed to downgrade my project from unity 2021 to 2020. Upon build I receive hundreds of console errors

"Objects being deserialized is from a more recent version of Unity. This is not supported and objects will be skipped."

Does anyone know what might be the source of this error? When I click on the error no further information is given such as file location. This doesnt seem to effect anything from I can tell because the build succeeds. Everything seems to function in editor the way it should so I'm just curious if there is a way to get rid of these errors for good. When switching to 2020 I did delete my library folder and let it regenerate before working in 2021 and I fixed any other script errors and package incompatibilities.

 

Unity doesn't support downgrading projects at all.

Seems pretty straightforward. They were serialized in the 2021 version and you're now trying to deserialize them in 2020. This presumably goes for any and all of your asset files (scenes, prefabs, other assets)

Yes, you downgraded your project, which is not supported.

 

Ya i understood going into the downgrade process that its not actually supported by unity, but I've read plenty of other cases where people downgraded their projects with varying degress of success. Unfortunately there is a bug in 2021 that really doesnt have a fix (inconsistent deltatime) so I was willing to take a risk in downgrading because it severely effects my project quality.

Looking at the full error closer it says this:
The list of [SerializeReference] objects being deserialized is from a more recent version of Unity. This is not supported and objects will be skipped.
(I left off the beginning "The list of [SerializeReference] objects". Not sure if that makes a difference.)

As a relatively beginner dev, Im not really sure what this means. so any further explanation would be helpful. You mentioned it effecting any and all of my asset files but I dont appear to have any issues with my assets, nothing has gone missing and appears as it did in Unity 2021. When I press play in editor I dont have any console errors, the game plays as it did in 2021. The errors only appear after a successful build.

 

Not sure what you didn't understand about the explanation. Unity has serialised data (written to disk) in a way in 2021 that isn't supported in 2020.

Namely Unity did an update to SerializeReference in 2021+ to improve the serialisation some. Naturally this cannot be back-ported to version of Unity before this improvement was done. So, find the affected assets, and re-enter the data.

 

but how do u find the assets