I understand that the grid owner can set local chat to region wide.

Thanks Rhowin.
That works!

I know I've seen one in my recent hypergridding, but here are two in the public domain:
- Wizardry and Steamworks: https://grimore.org/secondlife/local_chat_relay/simple
- SL Wiki: https://wiki.secondlife.com/wiki/ParcelChatRelay