Unable to archive Time Capsule using Airport Utility, "No AirPort disks available"

You must have missed the instructions that I provided in your other earlier post.....linked below.....to connect the USB drive to the USB port on the Time Capsule. That is the whole purpose of the Archive process.

https://discussions.apple.com/thread/252574554

Glad the process did not require extra equipment.

The hard drive connected to the USB port on the Time Capsule needs to be formatted as Mac OS Extended (Journaled), so you have that covered. FAT 32 should work as well, but the Mac format is preferred.

If your Mac can "see" the Time Capsule disk......named "Data" by default......then it should be able to "see" a drive connected to the USB port as well if the planets are also in nice alignment.

We will assume that the USB 2 port on the Time Capsule is working correctly.

The USB drive cannot use any type of encryption or "protection", so that would be one thing to check

The USB port on the Time Capsule is underpowered, so it is often necessary to use a powered USB hub with the hard drive.....even if the hard drive has its own power supply.

For example, I cannot connect my Lacie USB drive......which has an external power supply.....to the USB port on the Time Capsule and have it recognized..... unless.....I also use a powered USB hub.

If your USB hard drive is USB 3, that is supposed to be backwards compatible to the USB 2 port on the Time Capsule, but Apple has not changed the hardware on the Time Capsule in many years. A powered USB hub might allow things to interface when they otherwise will not.

Not sure if you are aware that the USB port on the Time Capsule will run at about half the normal speed of slow USB 2, so things are going to be S.....L.....O.....W when they are working.

Samsung T7 is SSD and at 2TB is very big (and expensive) but it is likely too new for the old A1409 USB which has limited speed USB2 and limited current. Older USB is limited to 500ma.. do check the T7 rating for current.. I could not readily find the spec but my guess is it will need 5v at 1-2A. No way a TC can supply that much.

You might be more successful with a powered USB hub between the TC and the Samsung T7 .. but beware as not all hubs will work either and especially since the Samsung has USB-C chip in it..

Speed of archive to disk is woefully slow.. I recommend a rather ordinary plain old WD passport or the like. They are better drives for mundane purposes where the speed advantage of SSD is not significant.. and especially for backups where lots of sectors are rewritten at a rate that SSD are not so good for.

For what its worth, I have a few older WD "Passport" drives here and they work just fine when I connect them to the USB port on the Time Capsule or AirPort Extreme without using a USB powered hub.

Apple's terminology can be confusing at times, but an "AirPort Disk" is a disk or hard drive that is connected to an AirPort router.......an AirPort Time Capsule or an AirPort Extreme.