How do I recognize in DTTG4 whether the data in the databases are encrypted?
You can’t detect that, as there is no such thing (per the DEVONthink ToGo Manual in Section “Specialized Databases”:
Due to the differences in filesystems between Mac and mobile, the encrypted databases in DEVONthink aren’t supported.
There is more in the DEVONthink ToGo Manual and I won’t repeat here. Take a peek.
Sorry, I didn’t ask correctly. I mean the databases synced to the iCloud.
I don’t have experience with encrypted DEVONthink databases. Too finicky for me, so I use other methods. I assume they can be synced since you are asking about them. However, I do understand that the files DEVONthink puts onto third-party sync services, e.g. iCloud, for you are optionally (but recommended to be) encrypted when you set it up, and those files are not DEVONthink databases. So if you turn on encrypted, those sync files (not DEVONthink databases) will be encrypted.
As to how encrypted DEVONthink databases residing on the local file system are sync’ed to, say, an iCloud sync store that you don’t encrypt … I don’t know and must defer to others for comment and/or correction. @Bluefrog ?
Perhaps there is something documented in the DEVONthink Manual–not handy to me at the moment to check for you.