I unfortunately just ran into this issue as well. I have a university issued iPad that I do my main work on, and it necessarily has a separate iCloud account from my personal devices. On my personal devices I can log into the Goodnotes app with this 'alternate' iCloud account, but it won't sync the documents because the devices aren't logged into the same iCloud account. I'm sad it doesn't sync because I love Goodnotes and want it to sync seamlessly! It seems like there should be a minimal implementation possible with other the backup options already available? (e.g. Google Drive)
I unfortunately just ran into this issue as well. I have a university issued iPad that I do my main work on, and it necessarily has a separate iCloud account from my personal devices. On my personal devices I can log into the Goodnotes app with this 'alternate' iCloud account, but it won't sync the documents because the devices aren't logged into the same iCloud account. I'm sad it doesn't sync because I love Goodnotes and want it to sync seamlessly! It seems like there should be a minimal implementation possible with other the backup options already available? (e.g. Google Drive)