[best practices] managing LTS & release lines for userland modules

I'm starting a discussion in Mocha around how we can best support multiple "LTS" release lines.

I'm familiar with what Node.js itself does (though I haven't ever cut a Node.js release myself; it seems essentially like trunk-based development). But I don't have an understanding of all the gotchas around something like this.

It does seem that, without proper tooling, maintainers will be in for a lot of pain in addition to the extra overhead that the strategy initially incurs.

I also don't know how other teams/projects that want to do long-lived release lines do it, and would love to hear from them!

How can we, as the package maintenance team, help projects that want to take this on? What works and what doesn't?