With just this mod, kry-stdlib, and base (not space-age) the long-handed inserter recipe is free, i.e, has no ingredients.
This must have happened recently, first noticed yesterday. Its definitely present in:
base=2.0.72
kry-inserters=5.1.15
kry_stdlib=2.1.0

Since you do have settings regarding recipes, they are all standard. For completeness:
Costless long-handed upgrade: yes
Long inserter drops as long inserter: yes
Burner inserter fuel leech: yes
Classic multi-row menu sort: no
Enable additional burner inserters: no
Disable other long inserters: yes

I also know it to be present in 5.1.14 in combination with a lot of mods, but I did not isolate it to just this mod.

I believe the cause is in data/makeinserters:431:

if kry.norecipe then -- fixes vanilla long-handed recipe
Recipe("long-handed-inserter"):clear_ingredients()
Recipe("long-handed-pipe-inserter"):add_ingredient({name="inserter",amount=1,type="item"})
end

It looks like the second statement is intended to modify the same recipe again, compare to line 142.

Yup, looks like copy-pasted the wrong line there when converting the add_ingredient function, should be a relatively simple fix when I am able to update (in about 3 hours)