How can I fill a drywall hole in a corner?
Orders are actually easier than flat surfaces. In hour case I would see is i could slip some “paint stir sticks’ behind the sheetrock for support and hold them in place with 2 or 3 Sheetrock screws. For cases like this I use mesh like on the right for the back and let that dry with a coat of mud on it of corse.
Then 2 or 3 more coats letting each one dry between coats once you have it almost filled then paper tape in the corner and over the hole it may take a couple of strips. A thin coat of mud over the top let that dry and sand fill low spots sand high spots but with a little time you can have that hole sealed up and ready to repaint.
If you have never fixed a hole there are as many different ways as there are people.
I recommend folks new to tape and texture not use setting compound just standard Sheetrock mud it takes longer but almost every DIY first timer that used setting mud or Hot mud (it sets up in 15 minutes to 1.5 hours) has made a mess that I &amp; others like realtors &amp; landlords see when I enter the room.
Watch some uTube videos on patching holes but my advice is use normal Sheetrock mud and get at least a 6” mud knife and a hand sander with abrasive cloth or ~200 grit sand paper.