There are several podcasts about the Newbrain on the Floppy Days Vintage Computing hosted by Randy Kindig. You can check them all HERE .
Floppy Days 131 – Grundy NewBrain History with John Grant
Floppy Days 132 – Grundy New Brain History with Steve O’Hara-Smith
Floppy Days 133 – Grundy NewBrain History with Gerald McMullon
Floppy Days 135 – Grundy New Brain Tech Specs with Chris Despoinidis