We use Bitwarden[0] for our secrets. It's open-source with a hosted option. Makes sharing passwords and keys across the team pretty straightforward.
In addition to it, we use envwarden[1], which is a simple open-source wrapper around the Bitwarden CLI to manage our server secrets. It's super simple, but does the job for us well. We can then manage both passwords and keys in one place.
Disclaimer: I created envwarden. I'm not affiliated with Bitwarden in any way however. Just a happy customer.