What is the best way to keep cats off patio but won't hurt them?

Spray with hose

Cayenne pepper!

They're not fond of citrus scents. Plant a large pot of lemon balm or use citrus candles to deter them.

You can buy a sensor sprayer for to keep dogs out of your yard. They might make a similar one you can use on your patio

If you are out there, keep a spray bottle full of water on stream and squirt them whenever they get on the patio. Eventually they will be trained, at least that's what my mother did with her cat.

They make both a pet motion detector hose attachment that will give kitty a shower that deters them. And they also make little air cans with motion detectors. Relocate them periodically so they never know where its coming from..... https://www.amazon.com/s?k=motion+detector+pet+deterrent&i=garden&crid=13AJZVJF85LLC&sprefix=motion+detector+pet+deter%2Cgarden%2C213&ref=nb_sb_ss_fb_1_25