creating a json backupfile

[nohkumado]

Hello
i am trying to use a librem5, and pre-installed i have https://gitlab.gnome.org/World/Authenticator, unfortunately the import by QR code from google authenticator doesn't work....
so i decoded with https://github.com/dim13/otpauth.git the QR code... and wrote my own dart app to generate the codes, but now i discover, that Authenticator has a json import, compatible with freeotp+ json format...
so easiest would be now to generate that code, but i don't seem to find any docu on how that should be formatted?
easiest would be to have some example file? annotated would be even better?
If i still had some, not broken, android device lying around i could have exported the keys with your tool, unfortunately i haven't....
so thanks in advance!