@dar1LN Gave me the right idea for accomplishing this.
In my case, I had Ubuntu installed on a Rock PI 4B and had installed Umbrel via the curl command, and it used my device’s hostname: rockpi4b.local by default.
Chaning my device’s hostname via:
vim /etc/hostname
and restarting the device did the trick.
Initially, I received the same CORS error reported above, but stopping/starting Umbrel (via ~/umbrel/scripts/
seemed to resolve that.