Do funds in LN channel get lost if Umbrel is destroyed?

I have Umbrel and I’m stuck with Error: No external drive found.

I had some BTC in the LN channel and I want to know if these funds are lost if I will not manage to resolve the SSD issues?

Thank you!

No. As far you have saved the 24 words seed and did a LN channels backup, you are good to go to replace / fix the external drive issue.
Here is a guide about how to restore/recover your funds from a dead umbrel node

But that is the last resort. First you need to diagnose / find out what is going on with your drive.
Check the troubleshooting manual that can help you with more info. In special to run the debug log and see what really is going on.