Real fun problem here, I’ve done a fresh install twice with what seems like the problem starting after installing clientconfig but removing it doesnt fix the problem.
SKIP AHEAD - I found the issue and it was fixed by removing versionX. I dont know if this is a versionx issue or a conflict between versionx and clientconfig but I removed both and then the full manager came back.
Note - the full page would load for a second and then go mostly blank like the image shows and console shows pretty much every resource is 404 (but again they load for a split second).
Hope this saves someone else some trouble and having to reinstall modx.