Do you have the 8GB RAM version? 4GB and Umbrel gives you a sluggish experience.

If you want to run your own LN node and/or BTCpayserver, save yourself the hustle and switch to Raspiblitz. It has zram activated by default and can operate with 4GB physical RAM, still you're looking at a steady load of about 80% to 90%.

I tried mynode, umbrel and raspiblitz and RP is the most advanced.