This commercial plugin is still a viable option to cover all shipping needs.

I've been using it forever and there is almost no scenario it cannot deal with.
This is not advertising but fact.

The code is excellent due to the superb efforts of the original creator Conor Kerr (RIP) but the subsequent development/support has been "inconsistent", for multiple reasons.

Since there is no chance I would ever drop this plugin, I have a private GitHub where I was maintaining just patches for the current version, but I've now gone much further to spring clean many files, which hopefully will be incorporated by Ceon Support at some point, or not. Whatever.

Current users can pm me for access if they wish to post issues or improvements, or can post issues here to reach the wider user base.

Aside: the discussion of commercial offerings was not permitted previously. I believe that to be now moot. Users should be aware of what is still available out there and if it's good or bad.