With that said, the problem still exists just one layer higher. If they are secrets, I use Infisical (https://infisical.com/) which is free and self-hostable, and let's you inject secrets at runtime via their CLI. Very handy for small teams.
On top of that, I use direnv (https://direnv.net/) with a hook to infisical's export command. This means when I 'cd' into a project, infisical runs and injects the secrets for my developer environment.
Everything that isn't secret just lives in .envrc and gets loaded by direnv, and you can just send those files however you want because they aren't sensitive.