Why not just mount the second drive and symlink it to wherever your Bitcoin Core data dir is. Don't forget to set auto mount on boot.
I did this with Umbrel and it worked fine besides borking with every update🤦♂️
Discussion
I'm new to this, lol, I think I've made some progress....
As long as that is actually writing to the external drive Good job!
Umbrel and Start9 both provide nice GUIs and preconfigured apps but are full OSs.
It is, thankfully, I had a small set back yesterday with wifi failing and trying to get bitcoin going again..... finally back up this morning.
I couldn't have done it without Grok, honestly. Tried using Venice for some help, but the experience on Grok was light-years ahead.
Loving Linux/Ubuntu so far. 1 week in.