Disk utility lack of encryption that will work with Time Machine

andybelinka wrote:

2. I have now tun out of space on that hard drive (TM won't seem to overwrite the older versions) So...

It's probably too small. If possible, make sure your backup drive is 3 times the size of all the drives being backed up.

3. I want to move the oldest backups to another hard drive (a 4TB seagate Expansion drive) to free up space. But...

Don't try that. It's a total waste of time. If your backup drive is too small, this is always going to happen eventually. Just erase the drive and start over. Since it is too small, ideally you want to get a new drive and start using it. Then you can erase the old drive and have two backup drives. Or maybe one backup and one archive.

4. when I format the Seagate hard drive as APFS encrypted and then try and move/copy the folders in finder from one drive to another, I get an error message dialogue box saying it is the wrong format for backups (or something similar)

On older versions of macOS, you could pre-format and even pre-encrypt the Time Machine volume, but that isn't possible anymore. Time Machine now manages its own formatting. Just format the drive as APFS or macOS Extended, whatever is the default, plug it in, tell macOS to use it for Time Machine, and then tell Time Machine to encrypt. A modern version of macOS will automatically reformat it as APFS Encrypted. The idea is that you just bought this hard drive from Big Box Electronics store and plugged it in. There is nothing else you need to do - plug and play.

Just so you know, the new backup will be significantly differently than the old Time Machine backups. If you go poke around, it won't be familiar. In fact, unless you use the official Time Machine interface, you may not find anything at all. Modern Time Machine uses local snapshots. If you just look at the backup in the Finder, it will always look empty.

Encrypt the partition: In the Finder, you can Control-click a Time Machine volume that’s formatted as HFS+ (Mac OS Extended) or APFS, select Encrypt, and enter a password, and the entire volume becomes encrypted.

https://www.macworld.com/article/353731/encrypt-time-machine.html

You and I can not Copy a Time Machine Backup Snapshot from one external drive to another external Drive

You are better off putting aside the existing drive for safe keeping

Then, setup the New " 4TB seagate Expansion drive " as New

How can I transfer Time Machine backups f… - Apple Community

As BDAqua points out, you can encrypt via Finder.

Or, the choice to encrypt TM backups can be made through the TM Preference Pane when choosing the backup disk and selecting the options for backup.

andybelinka wrote:

As I want to use the encrypted hard drive to backup my Macbook Backups. Time Machine will not work with APFS so what are we expected to do?

Can you explain this in more detail? I don't understand what you mean about "backup your backups". Time Machine also works fine with APFS.

andybelinka wrote:

Thanks. Some helpful info there. On the hard drive being too small, do you mean the destination drive that I want everything moved to? The one I was using for backing up my 500GB MacBook pro (Early 2015) that is now full, was a 2TB RAID. The one I wanted to move the older backups to is an empty 4TB hard drive. Maybe I just have to delete the older ones if there is no other way of doing it that will actually be any use.

Those seem plenty big enough. But it's the same solution. When Time Machine flakes out, just erase the drive and it will be fine again. If your Time Machine drive is too small, it just flakes out more often.