I think `pass` has an official extension to handle OTP, but here is how I do it:

  #/bin/bash

  clip $(oathtool -b --totp "$(pass show otp/$1 | head -n 1)")

Basically there is a really handy utility called `oathtool` you can install that has all the one time password logic built into it.

Then in my `pass` store I have a `otp` folder where I put the codes for my different services.

So to get the OTP code for paypal for example, I do this:

   pass otp paypal

And then the code is copied to my clipboard and I can just paste it.

Pass already has OTP. It is usually in the pass-otp package, both the Android app and the browser extensions support it as well.

Bitwarden does TOTP generation and is open source (also has a CLI tool), but I do not know if it would fit your use cases and needs.

gopass[0] is more or less a superset of pass written in Go that will do this for you. I’ve been using it for a few years syncing between iOS and macOS with no issues.

[0]: https://github.com/gopasspw/gopass