I have just had a look at the regular bulletin emails from the GHDL mail group.

There is a guy who is looking into creating a selected signal list that can be fed into GHDL !

This is fantastic news, I've emailed and advised that I have a large design that may be suitable to use as a test subject. Whether anything comes of the suggestion it doesn't matter. Someone is looking into the problem AND getting some success apparently !

By the way here is an image from the small testbench that looks just at the Trinity Net Rx in Gtkwave as a run on the Macbook.