I’ve generally used either an anchovy or a plain rubber patch (the type with the orange side and black side but not a feather edge) on the inside. That’s on the MTB. I’ve also just filled some deeper, but not quite through the tyre, cuts with super glue externally. Don’t know how long that will last but I’ll be patching inside too.
I have a bigger damaged area on one tyre where I’m going to try a bigger inner tube cut out.
I’m always amazed anchovies don’t pull out. I could see one in my front MTB tyre the other week flip flopping between the knobbles.
Gravel bike I’ve so far not needed to patch anything (famous last words) but I suspect a flat internal patch is the only viable option.
I keep meaning to get some mushrooms to add to the collection of stuff but most (not all) of my damage seems to be thorns and small holes that self seal.
The problem I’ve still not solved is a small amount of damage to the rim bed around a tubeless valve hole so the first 10ml of sealant ends up gumming up the base of the valve for a fortnight (and regular pumping up) after changing tyres.