I did actually get this to work but that was before taproot. AFAIK the bitcoin core no longer accepts GBT connections. I was able to do it with an older version of bitcoin core that did allow it.

I purely did it to see if I could. Nothing interesting happens cgminer reports a line every few seconds and that's about it. I had scratched that itch so moved on after about 10 minutes of watching.

It wasn't worth the effort to be honest. But was a rainy day and took a few hours of it away.

Oh and if you are tempted to patch bitcoin-core to get GBT working make damned sure you are on TESTNET.

Cheers.