I'd be fine with it if I get to see something unique and interesting done with the story. However, it might take some getting used to, as sometimes games change a legendary's personality completely and that usually messes with my perception of said legendary for a while.
Using deluxe battle I set up a wild battle with Galarian Moltres. I manually chose three moves for it by setting up an array like in the instructions, but the fourth move slot was automatically filled with heat wave, which is from Kantonian Moltres' moveset.
Please elaborate. The window appears then disappears? Or does the game window just never appear at all? Or does an error message appear before it closes? Do you make it to the title screen at least?
Assuming you're an Android user, you can follow this tutorial: https://eeveeexpo.com/resources/1165/
Note: Yes, that is a Patreon page, however you DO NOT have to pay to download JoiPlay!
Note 2: The only version I've confirmed to work with this game is JoiPlay 1.20.015 and RPG Maker Plugin...
I also seem to be having this issue. I'm using the version 20.1 version, by the way. I compared the essentials scripts to the one in this plugin and it seems like the only changes are changes to the positions of objects and text colors, so I'm not sure what could be causing the problem.