The problem I have with using a gMSA outside of Windows is you need a Kerberos principal and credential for that principal in the first place to allow retrieving the gMSA details. Why not just use that principal and avoid adding this next step.
It would be great if Linux had a mechanism where the host itself could act as the principal to retrieve the gMSA like on Windows but the GSSAPI worker model just works differently there and runs in process. A similar problem exists for using Kerberos FAST/armouring where Windows uses the hosts' ticket to wrap the client request but on Linux there is no privileged worker process that protects this ticket so the client needs to have full access to it.
The closest thing I've seen is gssproxy [1] which tries to solve the problem where you want to protect host secrets from a client actually seeing the secrets but can still use them but I've not seen anything from there to support gMSAs for armouring for client TGT requests.