As Raven said you can youse PkHex to trigger the event. I did the 3 nicknamed pokemon method and i still had the blackscreen. Now i just edited the file and hall of fame and after i turned on the game again I battle Hau
EDIT
After beating Hau the game crashes again. I tried to change the game language and the same result
This has been a known issue for a very long time. So far no one has figured it out/looked into it more. There is an issue ticket opened for it on Github. If there is any update to this issue, it’ll be there.
If that is an unofficial build, we don’t support that here. Only official ones.