Recovery every time triangle exclamation. 2018 Mac to shredder?

This from Packwood original questioner. The long four-month effort apparently will now end as I called Apple Support, and we concluded best to take it to a repair shop.

I had erased the drive and tried install from bootable Mojave installer, same Recovery error.

I used Target mode from my (this) MBP, it offered the Mojave Install but had to first connect to wifi, which ended again in Recovery error.

In response to John Galt on June 24 above, I called Apple Support, receiving very skilled, patient, hours-long expert help from RK, then Paul, then Harry.

Paul said I'd need to use Configurator, only available from another group so got Harry.

After much more expert, patient, hour long help, he finally concluded I must either:

1. Upgrade my MBP from Mojave to Monterey so I could run Configurator on it. Recall this entire problem on the Mac Mini was caused/started by me using Apple online to Upgrade from Mojave to Monterey. I was very reluctant because of that to upgrade to Monterey, and also because this MBP on Mojave can still run Adobe Creative Suites CS6 including Indesign, Photoshop and Dreamweaver that I still use.
2. Take the Mac Mini to a local Apple-authorized repair shop--- which I did yesterday.

I'm shamed and humiliated to take take a Mac to a repair shop after I've been buying, using, repairing, administering the dozen Macs in my newspaper business since 1984, when Macs first came out.

But presumably this four-month effort will end when the Mac Mini comes back from the shop. (After I reinstall all my apps).

By gosh you're right, first one 128k released 1984- that was my first Mac. My second was the 512k that I think we called "Fat Mac". I still have my SE which was a marvelous upgrade, first one to have hard drive- the last time I tried it, it would still run and go onto my network! Though SE was just BW screen I produced the first full color image that was printed on our newspaper printer's press- ASTOUNDED them!

Thanks for your correction!

THANK YOU THANK YOU!! I'll try your process probably later today.

All my bootable installer drives were made on my (this) 2019 MBP which is definitely capable of every OS from Mojave (safely running now) to Ventura.

Tried your steps twice, w Options down, on 2d try it did offer Install Mojave from the USB bootable startup drive, but when clicked it again started Recovery ending in triangle exclamation mark.

I've waited the 10-min Recovery start at least three dozen times in the last few days and am just unwilling to do it again.

My Mac Mini has two 500G drives, the second one (non-erased) has 300G of stuff I want to retrieve, so will try Target Mode to cc that stuff onto a USB flash drive or to Dropbox. I don't like iCloud which doesn't work as Documents folder as well as Dropbox or sync.com. Will require big USB flashdrive & USB-C male to male cable that I'm not sure I have, but will move toward that.

I see on Apple Store a Refurbished Mac mini Apple M1 Chip with 8‑Core CPU and 8‑Core GPU

$469.00. Probably will buy that and put my Mac Mini in shredder. Apple's upgrade to Monterey destroyed it.

Thanks. I will try some more, Apple Support next week.

I am trying shift-command-R for original OS of computer that I hadn't tried before. Taking a much longer time to start Recovery than ever before.

Sincerely, thank you!

I'm writing here on my MBP- the subject computer can no longer be started to normal finder. So I can't do "About This computer" or anything normal like that. It only starts to Recovery always ending with triangle exclamation mark, or Target (I learned two days ago). I don't have but have ordered the USB-C to USB-C cable, arriving Wed..

According to my record it is:

Apple Mac mini "Core i5" 3.0 (Late 2018) Specs Mac Mini MRTR2LL/A Ser# C0***YVY quadcore8thGenIntelCore i3 3.6GHz 10.14 (Mojave) 16GB DDR4 (Bus) 2666 MHz 512GB SSD

Everymac says: This model does not support internal hard drives.

I don't recall adding the additional 500G drive (and doubt that I did) so I don't know how it is there except it must've been there when I bought it, but I do have 300GB of valuable info on it.

I presume when I get the Target cable Wednesday, I'll be able to install Mojave on it Thursday and all will be well, except I will have lost and must reinstall all the apps I had on it which included all of (almost fully usable in Mojave) Adobe Creative Suites CS6 for which the installer DVD was trashed when we closed the business last year. But maybe still on a TM backup?

[Personal Information Edited by Moderator]

Thanks, John. Surely it’s easily repairable- an erased drive just needing OS installed without triggering Recovery that ends in error.