FYI, @KaiClavier, it looks like there is a bug that is ominously closed "ByDesign" here: https://issuetracker.unity3d.com/issues/cannot-enable-emission-when-using-materi...
However, I found a fix for this. I looked at your shader "Super Text Mesh/Unlit/Default", and see this:
[Toggle(SDF_MODE)] _SDFMode ("Toggle SDF Mode", Float) = 0
So I tried a:
mat.SetFloat("_SDFMode", [0/1]);
Instead of your EnableKeyword/DisableKeyword calls, and now the material properly toggles in the editor (and I see the SDF pass for example changing things, so it seems to function). I don't know why Enable/Disable keyword doesn't work.
PS I did see you reply to my subthread reply earlier in the main thread (I guess I'll keep to the main thread).