Here is a great tip for Core Lightning node runners.
I have found that the automatically chosen fees when performing a cooperative closing are too low to confirm quickly during these times of high fees. Here is how you can close a channel and specify a fee:
lightning-cli -k close id= feerange='["52000perkb", "96000perkb"]'
This says to offer your peer (who is currently online) a range of 52 to 96 sat/vB. I found with another Core Lightning peer that we agreed upon the low fee that I offered so you should expect the same.
I find that I would much rather have any lightning related transaction confirm within a block or two rather than leaving open the possibility for fees to jump and have a channel end up in a limbo state.