I recently upgraded hardware, and the new machine came with MacOS 10.14 (Mojave) installed. Following the OpenOffice installation instructions, I downloaded and installed AOO 4.1.7 on this machine with no difficulty. Following Oracle's Java installation instructions, I downloaded and installed JRE 1.8.0 with no difficulty. OpenOffice can find and use Java. This took about 20 minutes, excluding download time. (A summary of installation procedures is located in [Tutorial] Mac FAQ Q03/A03, Q05/A05, and Q06/A06.) I copied my documents from the old machine to the new one using an external drive. I can open documents, including password-protected ones, on the new machine with no difficulty. I did not need to make any of the adjustments discussed in Q15/A15 or Q39/A39. No documents are in read-only status (Q16/A16).
I am waiting and reviewing reports in the forum of experience with MacOS 10.15 (Catalina) before installing it because Catalina was released on 2019-10-07 which is after OpenOffice 4.1.7, dated 2019-09-21. I think it is wise to wait for at least one OpenOffice release after a MacOS release before installing the MacOS release. I do not use LibreOffice.