What to do when you can’t directly copy Time Machine backups
Apple continued the Apple File System for several years. In macOS 10.13 High Sierra, this format is sufficient for Time Machine to copy files to APFS-formatted drives. So far only the classic HFS file system has worked. And still working scanners usa on this system.
Apple created a new APFS disk type or "role" called "Copy" in the APFS cipher. Because it's a dedicated partition, you can't simply copy a Time Machine backup from one APFS disk to another like you can from one HFS volume to another. (You certainly can't copy from HFS to APFS or from APFS to HFS!)
What if you want to migrate an old APFS-formatted Time Machine drive with historical archives to a newer drive? You have a few options, nothing fancy:
Keep the old drive: Keep the old drive offline for at least a few months so you can download older versions of files by plugging it in and using Time Machine to check its archive or mount disk images to browse specific backups.
Restore a backup to an external drive: Use another drive (or drives) with Migration Assistant to make a Time Machine backup for a period you want to keep before Time Machine backups.
Copy folders from backups manually: Use Time Machine while your current drive is connected to find suitable points in the past where you want to capture old versions of files or even folders containing deleted files. The easiest way to do this in the Finder is to navigate to a specific snapshot and then explore the folders you want.
Does Apple allow you to clone Time Machine backups from APFS drives or copy photos? That possibility seems remote at this point, as Apple had plenty of time to update Disk Utility or command-line tools and release the information to third-party developers, but decided against it. However, Cloner Carbon Copy Software Bombich Software, developer and file system guru Howard Oakley, and other software developers are open to expanding Time Machine backups if Apple publishes the necessary documents or tools.