What is the safest way to store and share a permanent username and password?

In a similar use-case to #51, there are situations where I find I want to store share a password with someone that _should not_ be changed afterwards as both people will need access to that password in future.

An example use case for this is a password-protected document (accountants and lawyers share password protected documents all the time and usually drop the password into the email which includes the document 🙄) or from a personal perspective, household utility supplier accounts.

There are [many password managers](https://www.pcmag.com/roundup/300318/the-best-password-managers) out there but I couldn't find one that is open source or that I trust to not go under and take all my information with them (or sell it off) because I don't have much experience with these.

Any thoughts on what people already use or have tried?