A bunch, ranging from JS to Clojure and everything in-between, depends on the project.

The approach also depends on the project. There is a bunch of different approaches and I don't think there is one approach that would work for every project, and sometimes I requires some wrangling but takes 5-10 minutes tops.

Some basic information about how you could make it work with 1Password: https://developer.1password.com/docs/cli/secrets-environment...

How long have you been using that method? I didn't feel it's been very popular so far, although it makes a lot of sense. I've always seen people using gitignored .env files/config dirs in projects with many hardcoded credentials.