In addition to the above, if scratching is the worry, I’ve had luck with a couple of drops of Petitgrain / Bitter Orange essential oil where they’re keen to scratch. The smell is strong for a day when you first put it on, so if you hate it, that’s not helpful - it doesn’t bother me. It will fade over time, but I’ve found that that the deterrent is usually good for several months before they rediscover the location as a desirable scratch.

I also regularly (about once per week) mist where I do want them to scratch, their scratching posts, with catnip spray.

And finally, for a couple locations that they seem to always be super attractive for scratching, and are also out of the way (the backs of two fuzzy armchairs which are in corners on an angle, so a dark space for a cat to get into), I’ve covered them in double-sided sticky sheets sold as scratching deterrents, and that’s solved those as problems. This might not work as well on the side of a mattress that’s exposed, though.