Besides being able to store my Umbrel seeds on paper in a safe, how can I use them as an alternative?
Do you have a hardware wallet you can suggest?
You could of course enter the seed generated by Umbrel on any hardware wallet but what is the point? The seed is still on your Umbrel machine accessible by anyone with your Umbrel password that have access to the machine (locally, externally with the onion address or with your IP if you open up the UI port in your router, which is not recommended of course).
If your purpose is to be able to spend on chain from the hardware wallet, this will not add much security. You better use Zeus to connect to the node to be able to fully interact with it.
If your purpose is to make your node more secure by signing transaction externally, I’m afraid it’s not possible. I wish there would be such solution but I guess it’s technically not possible (now). I also hope there will be solutions for this in the future.