Recently I set up sync via iCloud (CloudKit) between DEVONthink 3.6.3 and the brand new DTTG 3.0.4 on an iPhone 12 with the latest OS (14.4.1). (I opted to download all rather than on demand.)
Absolutely none of the rtfd documents can be displayed in DTTG 3!
(But all regular rtf documents work fine.)
Attempts to view an rtfd document in DTTG 3 results in the generic:
Clicking on “Download (2 MB)” only gives me: