I was having the same issue... and posted this same question months ago with no response. I have since done a ton of research and this will NOT be possible with the latest version of this APFS driver.

The message is a red herring in once sense, and in another it is not. It can not mount in read only or read-write due to encryption but it has nothing to do with software. The issue is the new T2 co-processor chips they use for security in the MACBook of any kind after I believe 2017 when they were using the T1 co-processor chip for security. The new T2 chips do a hardware level encryption of your device that is supposed to work when mounted if you saw the request for a password.... but it doesn't. It also cannot be disabled, at least nothing that has been published or that Apple Support will give you. After months I assure you I am 100% correct. I also verified with another product that is supposed to deliver the same mounted drive but in read only mode as that won't work either.

I am currently working with Paragon Support but it is going to take a change in the driver software to have a shot. Your only option is to create a partition that is not APFS and store your files there.

Jim