It’s a well-known drawback of Plasma Wayland session, you cannot disable these built-in gestures until they add the respective config option. I believe there’s plenty of bug reports on this, just too lazy to look them up. In brief, you need to “thank” KDE devs for this questionable decision…
PS: I guess even Plasma 6 won’t have a switch-off for it – at least I haven’t seen them planning this.
If this is in Wayland, there is no options to configure it, at least not via GUI. KDE devs are aware of that problem and are positive about adding it, but it has a low priority and there is no one working on that, last I heard. I could be wrong, thou. I hope I am wrong.