Difficulty with TextMeshPro after updating Unity to latest

I have a considerably sized project that has been on the same version of Unity since 2018. I tried updating to the latest Unity today, expecting a lot of errors – And was met with a lot of errors.

The first wave are all related to textmeshpro:

image of errors: Imgur: The magic of the Internet

There’s a long list that are similar to these. I tried updating TextMeshPro to the latest using the package manager and the same errors persist.

Any ideas about what to do?

Maybe this thread may help?

I don’t think that can be the issue, since that thread is from january 2018, and my functioning version of unity/tmpro is from mid 2018.

What version of Unity and TextMesh Pro are you upgrading from and to?