When I closed out my channels, this is the suggestion Alby made:

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The best way to close a channel is to do it while it is online, click on the 3 dots on the right (see screenshot), then execute a normal closure (Not a force closure).

The funds on your channels will go to your Savings Balance (which is the onchain side of your Self-custodial wallet).

Then you can withdraw the funds from your Savings Balance just as any other onchain transaction.