A "patched" Nintendo Switch refers to a console where the original hardware vulnerability (RCM exploit) has been fixed by Nintendo

If you see “patched” in a listing – assume no modding . Buy only if you want a pure, unmodified Nintendo Switch experience. For hacking, search specifically for “unpatched Switch” or check the serial number before paying.

If you're a Switch user who's concerned about the patch, there are a few things you can do:

If you are asking about a "patched" Switch (consoles built after August 2019 like the V2, Lite, or OLED), these cannot be modded via software alone.