Well to see if it’s a bug with this version. If you try with let’s say 4.20 and you can create a camera in an empty project, I would just reinstall the engine version 4.21. Maybe recompile.
I tried at work, and I can create cameras in the vehicule template versin 4.21, so it may be a bug.
If you want, you could upload the project and I could look at it.