I use practical security measures that match my level of exposure and don't severely limit my convienience.
If your lab isn't exposed directly to the internet, at the very least update your servers from time to time, use a string root (admin users as well) password. That's more than enough.
If your lab is exposed, the same applies but update more often. Use SSH keys.
Don't go overboard - the majority of security incidents are from lack of basic security
Just be careful how much you depend on the git repo for Flux.
I made the mistake of doing the same thing but took it a two further and used Gitea for my container images and helm charts. When I messed up Gitea during an ArgoCD sync, I couldn't roll back because the custom helm chart for Gitea and Postgres came from Gitea.
It also messed up every other application and ended up deleting all my resources during auto sync.
Best thing I ended up doing was mirroring Gitea to GitHub, including images and charts. Then using that for ArgoCD.