Secrets Management? Alternative to Hashicorp `Vault`?

We need a way to _seamlessly_ share highly secure secrets as a Team.
Specifically if more than one person in the team is testing the `Auth` App [running on `localhost`],
there will are at _least_ 10 evironment variables to be shared: https://github.com/dwyl/auth/blob/main/.env_sample
We've done this in the past by sharing a `.txt` file via [`Signal`](https://github.com/dwyl/learn-security/issues/68).
This _works_ in a pinch because it's end-to-end encrypted, but it's really not a good way of doing it. 💭

At companies we've worked in the past the DevOps teams have used Hashicorp `Vault`: https://www.vaultproject.io

Just signed up and to launch a `Vault` instance is `$25.92/month` ...

Just to store secrets ... 💸
Feels like this should be a Serverless App that only runs when people are _using_ it.
Is there _already_ a way of doing this where a Serverless App stores data _strongly_ Encrypted on `S3`
and has strong access controls and team management?

Need to make time to investigate this so that sharing secrets with new team members is faster. 🚀
For now just going to continue using the `Signal` approach ... 💭