I think the reason my secure_ssh.sh script creates users with just a $ prompt is because I probably missed a flag for useradd. I should probably have read my own CentOS Notes better.
Since my techjournal repo is basically just the markdown pages that create this website, and I don't think I would necesarily need this particular SSH key or script, I put the linux/{centos,public-key} stuff into the Git repo made specifically for my Docker project, which you can find here
On the off-chance that I do ever decide to reuse the script, I used curl within it to grab the pubkey, rather than assume that the user has git and has pulled the whole repository. This also makes more sense in my mind because the user might not actually want all the Forgejo docker compose stuff. (Although, I do think it is pretty rad)