Turn off the LND node

I have about 40 channels.
If I decide to turn off the LND node, I must close all channels, and I will lose a lot of sats.
How to proceed in this case?

Do you just need to power off your node? If so, then just use the shutdown option in settings. Your channels will not be lost.

I meant to shut down the LND permanently

When closing a channel, I’ve heard it’s best to use ThunderHub which allows you to set the closing fee. If you close with the Umbrel User Interface, it closes the channel at a very high fee that’s not (yet?) adjustable.