I recently started playing Pokémon: Let's Go, Eevee! in Japanese, and I have seen this grammar come up a few times. Most recently in the following dialog.
この ポケモンジムは 閉まっとる
To me it seems as if the て was replaced with と, as in 「閉まってる」.
When I first came across this I tried looking up this structure, but to no avail. I couldn't seem to find anything on this type of grammar. Then I thought I may have just caught a typo and moved on. But after seeing the same structure pop up a few times I realized it must be something I haven't seen before.
I still cannot seem to find anything on this structure (maybe my googling skills just aren't up to snuff). Is this some verb form that I have yet to learn? Is it the と particle in an unfamiliar position? Or possibly some kind of dialect they're using?