If you're using multi-users in GrapheneOS, you'll find all the paths from the Daijishō index are wrong, this is because all paths need to be renamed in the following manner:
/data/app/->/data/app/~~[random1]==/com.retroarch-[random2]==//data/data/->/data/user/[user_number]//storage/emulated/0/->/storage/emulated/[user_number]/
This project automatically does this for you, generating a directory that you can host yourself.
Be sure to have NodeJS installed in your machine, and just run the generate.js script with the following arguments:
node ./generate.js [user_number] [random1] [random2] (optional: server_url)
All these arguments can be found by running RetroArch, and seeing the app logs (Apps > Retro Arch > Application info > View logs), and searching for data\/.
After executing, an out/ directory will be generated. Directory that you can upload to your own github repo, or serve through a local server in your phone (with an app like Transfer for example).
If the Daijishō platform index gets updated, let me know with an issue.