Samsung Portable SSD T7 partition greyed out so cant set as boot drive with Monterey

i have a T7 SSD that i use to run catalina when i need to. i was able to erase it without issue. in disk utility, are you sure that you trying to erase the drive at the top level of the drive?

i still have the option to erase / reformat when the top level of the drive is selected.

also, erasing the drive at the top level of the drive also erases any preloaded software that is supposedly installed to make the drive "mac ready". samsung software has a known history of not working well with macOS. and if you manage to get that software working, any subsequent macOS upgrades / updates can cause that software to fail, leaving you scrambling for a solution.

and, i should have included the link to this informative user tip: How to Setup and Use an External SSD as your Startup Disk - User Tip. it is the instructions i followed to install catalina on my T7 drive.

andrewjohn63 wrote:

As far as I can tell I'm on the top layer

to ensure you are at the top level of the drive, first click the right facing arrow next to the drive's name so that it points downwards.

then highlight the FIRST name as seen below. this is the "top level".

you're welcome. however, i'm one who recommends to never use auto updates. i prefer to be able to "investigate" upcoming updates to prevent incompatibility issues with loaded software. the only auto updates i use are these:

andrewjohn63 wrote:

I just cant get the "SCHEME"option to come up.

it was so long ago that i forgot this. your reply reminded me. when i first went to erase the T7 drive, the "scheme" option didn't appear for me either. but i went ahead and erased the drive anyways. after that, i went to erase the drive again. once i went to erase the drive the second time, the "scheme" option was available. so i then formatted it as APFS with GUID partition map.

Here's MY query: I have a late-2015 iMac 27" (17,1), that's currently running High Sierra on an external startup drive (Samsung 870 2Tb SSD), connected via USB - DIRECTLY - to one of the four iMac's internal USB ports.

Also have a Sabrent USB 3.0 4 Bay 2.5” Hard Drive/SSD Docking Station with Fan (DS-4SSD) with four internal Samsung 870 2Tb SSD's, each of which I've formatted with various Mac OS iterations (Catalina, Mojave, Monterey, Big Sur) in order to run a plethora of legacy software programs which I've invested heavily in over the years, as well as current subscriptions and software that required the latest OS... but I cannot get my iMac to restart on any of them as the "startup drive"!

Do each of these drives need to be directly plugged into an iMac internal USB port directly in order to be recognized as a startup drive?

Is the fact that they're installed in an external, powered device - that itself is plugged into an iMac internal USB port - the problem that's preventing them being recognized/used as startup drives?

Thanks for all suggestions: I've been at this for days, now...

I still problem try formatting it on a PC and then see if you can successfully erase it on your Mac.