You dont want just the original version from cart? Assuming your switch is using mods, then re-install it without updating it anyway, only use the updates you want it to be at. (remove it, then install the base version again, then add an update for the version you want)
There's also a method that can use someone else's switch if they have the version you're looking for I think, but I haven't looked into it.
Is it that your firmware forcing you to update? I know for me I can still play the games just choosing not to update them but if you have later save data forcing you to you could try removing the save data, else if all else fails you'd have to either downgrade your firmware itself then, or I heard devmenu can do some things, like change metadata around the version. That's probably another way for things.