Converting an APFS volume (and it's partitions) to HFS+(non-J) without needing to migrate data

Paragon Software has a product called APFS for Linux. This would allow read/writing to APFS without have to convert to HFS+. Evidently, you have to build and install the driver. So this would in theory work with any current Linux distribution. The only drawback is the APFS container would have to be pre Big Sur. In other words, the APFS container would have to never had Big Sur installed. Currently, Paragon Software is working to overcome this limitation.

Update: In a comment, the OP posted there exists a read-only FUSE driver (apfs-fuse) available that might be Big Sur compatible.