Thanks @dom that’s solved it.
Specifically: Adding corepack enable && to build & start commands in render.yaml.
It then ran into memory issues during API deployment at the stage:
Installing plugin “@redwoodjs/cli-data-migrate”…
This seems to be solved by setting NODE_VERSION to 20 (from 18) as mentioned here
Thanks very much for your help!
Now the only issue appears to be my realtime functionality (via subscriptions) has gone missing. I may open another thread for this :bang-head-on-desk