SIP issues with an external drive

Did you try booting the external drive on the 2012 laptop while connected externally? If you have the non-Retina model, then the internal hard drive SATA Cable may be bad so booting it externally may be fine (assuming the drive is healthy & the OS/file system is ok). That is a common problem with the non-Retina model.

Which brings up the question, what is the exact model of this pulled drive including whether it is a 2.5" SSD or an M.2 blade style SSD, or an SSD using the Apple proprietary blade style SSD connector? We are missing way too much information. These are extremely important details.

I highly support @BDAqua's suggestion to check the health of the external drive making sure to post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar so we can examine the health report.

I am confused by this thread. I thought you were using the pulled drive externally on the 2017 Mac, but it also seems like you are trying to run First Aid on it or even erase it. You need to slow down and pick one thing to do. If the external drive is healthy and the USB cable/adapter and the drive dock, adapter, enclosure is working & compatible, then you should easily be able to erase the pulled drive by making sure you erase the whole physical drive by following the instructions in the following Apple article:

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

You also need to tell us exactly what happens in detail along with the exact error message when you try to do something with the external drive. I have seen no useful details posted in this thread which we can use to assist you.

In Disk Utility>View, select Show all Devices, highlight the top left entry.

Run Disk First Aid on all items in the left panel, from top down.

You can use Drive DX to possibly get a better view of Drive health…

https://binaryfruit.com/drivedx

Restore mode isn't essential, but sometimes helps.

Let’s see if there’s a locked file interfering.

Open Terminal & paste this command in & prefs enter, it’ll ask for an admin password & not echo what you type, wait for it to finish which will be an empty prompt unless it prints out some locked files, or Operation not permitted…

cd /Volumes;sudo find . -type f -flags +uchg

It is so rewarding! /s

I wonder how many others will decide to help out now with that attitude?

How many times have we seen my computer "died" or is "bricked", when after asking a few questions we discover that we were able get it working again? Or perhaps the issue with the old computer caused a problem with the drive as well. And we don't even know the condition of this SSD since the OP refuses to provide us with a DriveDx health report for us to examine since three of us contributors suspect a possible hardware issue with the SSD. But all we know is the old laptop is dead and the SSD is useless.

I'm going to leave this thread since I am obviously not wanted here....the OP seems to know more than we do, yet has been unable to resolve their issue. I don't need to waste my personal time here when so many others will appreciate some assistance. I wish you luck here.

Are you trying this on the 2021 Mac?

Are you trying to mount it or vrepairit in Restore Mode?

Mayhap the reason the MBP died was that its HDD died?

SSDs fail, too. Some failures will go read-only, some will vaporize.

An external disk shouldn’t need to use recovery mode at all, particularly if erasing and re-formatting the entire device.

Don't you just love being belittled for asking for clarity when trying to help someone?:(