Hey @Junkman,
The “Catostrophic Failure” error you’re seeing, we’ve been seeing reports from othes seeing that as well in the MonoGame discord.
That error specifically, if you look it up, there are tons of results that all point to different VS versions that eventually updated and got fixed.
I cant say 100% for certain this is a VS issue and not a MonoGame issue, but at this point im thinking it is a VS issue.
If you run the command
dotnet mgcb ./Content/Content.mgcb
from a command line/terminal within the project directory, outside of VS itself, will it build fine? If so, then its 100% something borked in Visual studio (most likely)(probably)
Also as a last question, since you mentioned you installed the MGCB Editor via command line, did you install the MGCB editor as a global dotnet tool using the -g flag? If so, it should not be global, see here for more info