Trouble upgrading SSD on 2015 13" MBP

Question

I have a friend who is trying to squeeze a bit of extra life from his aging 2015 13" retina MBP by replacing the factory SSD, which recently bit the dust (flashing folder.) At my direction, he picked up a 1TB Crucial P3 Plus (regular P3 was backordered, but my understanding is that PCIe 4.0 should be back-compat...) and one of those cheap NVMe adapters on Amazon. He performed the physical install by following the iFixit guide, but is not able to see any evidence of the disk's existence in Disk Utility after booting into recovery mode.

I am in another state and not able to help in person, but walked him through some basic troubleshooting steps that did not resolve the issue. He was running El Capitan(!) on his internal disk when it bit the dust, so the Internet recovery is for El Capitan. While Googling I came across an old thread on another forum that said High Sierra was the first version of macOS to add critical firmware-level support for third party NVMe drives internally. I don't know how true that is, as this is the first I've heard that claim and the person did not cite a source.

Assuming that IS true, our predicament becomes one of: his factory SSD running El Cap died running El Cap, and though we were ready to install Big Sur on the new drive, we can't do that if it's not visible in Disk Utility. How can we get High Sierra or newer installed in the "base system" storage (recovery mode, et al) in order to "see" the new SSD and move forward as usual?

If the firmware thing is NOT true, my next instincts were that either PCIe 4.0 disks are only backwards compatible if there is firmware to recognize them (I don't know if this is true or not) or the new drive may have been factory formatted as NTFS which is not natively compatible with macOS. Even then, I imagine it should still show in Disk Utility and be able to be formatted from there?

Failing all of that, he may have a DOA disk or adapter. We are trying to exhaust all other trains of thought before getting into the headache of returns and exchanges.

Thanks in advance for any help or advice on this one!

Answer 1

Crucial does not have any compatible internal drives for a 2015 MBP. See here. I get nothing when entering 2015 in the filter box. Apparently, a cheap adaptor was employed, which may be the problem.

As an alternative, you may want to try OWC. Note that at the time of this posting, OWC offered Apple Factory Original Solid-State Drives for your Mac.