Use some kind of citrus sent to keep them away. My friend has done it and it really works. Either lemon or orange flavor.
Hope it helps! - Bushra https://bushraslifestyle.com/
You need to add plants in your flower bed that cats dont like. I was always told lavender or lemon thyme. There could be more that work.
Since they are strays, there are no owners to talk to about their cats' wanderings. That means you have to handle the situation.
Essential oils may work, there are some flowers cats do not like the smell of: rue, lavender, rosemary, and pennyroyal. Planting a border of these may do the trick.
Some have put down pine cones and other rough surfaces they do not like to step onlike broken ceramics, gravel...
Another idea is to set up a motion activated water spray. It works on the principal of when a cat approaches your garden, it detects the body heat and movement of the cat and sprays at it. And they do not like to be wet, this also helps your garden with watering.
We had the same problem and realized they like to potty in dirt, mulch, sand, etc. We recently filled in around the plants with lava rock because they don't like walking on it and they don't like trying to cover their poo with it.