I'm not sure, but that error may mean that your LonaJoiPlay package is not made correctly, or you didn't follow install instructions in joiplay correctly.
On my modified switch running android, I just followed the dev's instruction video on preparing the latest version of the game to run in joiplay and it loads fine, even with Modified Mod Loader, ModGraphicsPath mod (dependency for ExtraLoadingScreens), ExtraLoadingScreens mod, and Modular Cheats Mod.
Steps:
- Extract joiplay template.
- Extract fresh copy of the game.
- Optional Step: Install any mods.
- Run game to generate INI files.
- Set WRITING_LIST to 1 in GameLona.ini
- Run game.
- Set WRITING_LIST to 0, COMPRESSED to 1 in GameLona.ini
- Compress entire folder into lonarpg.rga (standard .zip file)
- Copy lonarpg.rga file to Android SDcard.
- Install lonarpg.rga in joiplay.
- Make sure to use Null RTP.
Attached is the template I used.
Screenshot of joiplay-ready game files:
View attachment 2403559
P.S: And no, the joycon's don't work with JoiPlay sadly.