Disk Utility does not offer APFS formatting

You must select Show All Devices from the View popup menu. Then, select the device and Erase.

If you don't show all devices, you cannot change the partition map on the device. That device is probably MBR partition scheme and it won't allow you to erase to APFS. APFS must be on a GUID partition map.

WestKester wrote:

Yep, selected "Show all Devices", and the left hand column showed all the devices, including the two T7's, the one in question and the earlier one used as the Time Machine backup device. So, MBR partition scheme? All I see is as I mentioned earlier "Name" and "Format". No selection option for "Scheme"

You need to erase the whole physical external drive as GUID partition and APFS. You do this from the "Erase" tab within Disk Utility.

If this still does not work, then try erasing the drive as GUID partition and MacOS Extended (Journaled). If successful, see if you can erase it again to see whether APFS is an option.

GUID partition type should be used for all external hard drives and SSD these days. The only time to use an MBR partition type may be for USB sticks and SD Cards especially when they are being used in other devices like a camera (or with other devices....such as connecting them to a car or TV to play music or videos).

If you still have a problem, then disconnect all other external drives and run the following command using the Terminal app so we can see the drive layout for this problem drive:

diskutil  list  external

Another important item to consider is the age of your T7 SSDs. Were they all purchased at the same time or years apart? Regardless, is there any date codes or variation in model numbers listed on those drives?

What is the firmware revision of each of those T7 SSDs? If Samsung has a firmware update available, then you may need to apply it to the SSD which is not working correctly (I personally would recommend only installing a firmware update using another computer where the SSD is known to work properly just to be safe since firmware updates are always risky anyway and could leave you with a bricked drive if the update does not complete successfully).

I do know that some external devices are not compatible with an Apple Silicon Mac. When Apple Silicon Macs were first released, there were multiple posts where it was discovered that someone had two T5 SSDs IIRC. One worked, the other did not....the only difference was the date of manufacture since it used a different & older USB chipset in the one drive which apparently was not compatible with the Apple Silicon Macs. I don't recall the specific details. I have personally experienced certain devices not working on Apple Silicon Macs, but working perfectly fine on older Intel Macs running the exact same versions of macOS.

Also make sure to connect the drive directly to the Mac and disconnect all other external devices in case one of them is causing a problem. You may also want to boot into Safe Mode to see if you still have the issue.

Edit:

the one in question and the earlier one used as the Time Machine backup device.

Was this SSD which isn't allowing the APFS format as an option....did it used to be a TM backup drive? Did you remove it as a TM backup drive through the Time Machine app? I don't use TM, but have seen some people mention that a drive must be disassociated from TM before it can be re-used again. If not, and if it is no longer possible to do so, then you may need to write zeroes to the beginning of the drive, or use a Windows PC to first erase the drive before trying Disk Utility again. Disk Utility can get confused if a drive has been used for other purposes in the past and this may be the only way to allow Disk Utility to work properly with a drive again.

What OS installer are you booting into? If you are booting into a macOS 10.12 or earlier installer, then APFS is not an option. On some Macs no matter which keys are used to access Internet Recovery Mode, some Macs will only be able to access the online installer for the OS which originally shipped with the Mac from the factory. Theoretically on Intel Macs, booting into Internet Recovery Mode using Command + Option + R should give you access to the most current macOS installer compatible for that Mac.

FYI, it always helps to provide the exact model of the Mac when asking for help online. You can get this information by entering the system serial number here:

Check Your Service and Support Coverage - Apple Support

Select GUID partition scheme, then APFS format.

As soon as you change the scheme to GUID, you will be able to choose APFS as the Format.

That is what other posters have been telling you, and now you can act upon their advice.

but if I click on "Samsung PSSD T7 Media" I get

That's what I told you to do a while back, select the device then erase.

Matti already answered your question correctly. You have to change the partition map first.

WestKester wrote:

I am left wondering though why the External Storage Device is differentiated from the media in the device. Looking here I have this box which contains the storage media, the SSD, and they are one and the same. However, I guess maybe this is a hangover from the dim distant past when we had an actual disk drive, into which you inserted the media, the floppy disk, or CD, whatever.

Technically your external Samsung T7 SSD is made up of two major components. A drive enclosure (the physical case & I/O board) plus the actual SSD itself. It is just that Samsung pre-built the complete set for users so to an end user the T7 SSD appears as just a single item unless they look deeper.

tkemathaba wrote:

mine is an Apple SSD, it doesn’t give me that option even when I have selected GUIDE scheme

It is unclear what exactly you are trying to do. The only Apple SSD are the ones built-in inside Macs. These are usually the ones used for booting. You cannot format the boot drive while booted from it.

I think it is better if you start your own thread and give specific details about what you are trying to achieve. And also, include screenshots from Disk Utility to help better understand what you are doing where.

Links from Apple on Disk Utilities usages

Erase and reformat a storage device in Disk Utility on Mac

File system formats available in Disk Utility on Mac