Install from micro SD Card in USB SD Reader/Adapter

(foreward - I DO know how to create the install image medium - this is just specifically about why it does not work on a microSD Card in a USB adapter)
This is a Minix U9-h running 7.1.2 Android - no issue with installing CE from either micro SD Card slot or from USB port with a ‘regular’ USB thumb drive stick (4GB)
I have tried to format micro SD Card through several different methods - initial FAT32 Format through DISKPART, Rufus, SD Formatter - then making bootable image through Rufus, Win32diskimager, Balena Etcher and even usb writer on linux system - used two different micro SD cards, both 16GB, both HC, one Samsung Evo, the other PNY Elite;
Neither card will boot from USB Slot in a USB/Adapter/Reader - it always goes to recovery menu.
I can boot with a prepped regular USB Stick in the USB slot and I can boot from the micro SD card slot - just not with the micro in the adapter.

Is there anything particular that is preventing boot from that combination i.e. micro SD in a USB adapter that I’m missing?
The adapter I’m using is a Kingston MobileLite G4

p.s. I just tried this with an SD card (not micro) with same adapter and IT boots - so there is some quirk about a micro SD card in the adapter not being recognized as a bootable drive?

MicroSD and SD are basically the same, only different form factor.
Kingston MobileLite G4 is dual adapter
Maybe the MicroSD-slot is damaged, as the device works with SD-card.

I don’t think anything wrong with the adapter slot - it reads normally except for the booting issue
I have another adapter coming tomorrow - we’ll see if makes difference

There are some construction differences in various “USBtoSDcard” devices. I have 2 of them, Kingston MicroReader (FCR-MRG2) and Kingston MobileLite G4 (same as yours) With later my N2 installs and boots from all my uSD and SD cards, and with the former my uSD cards are not even recognized in any USB input on N2. So maybe your uSD slot on MobileLite G4 is faulty/dirty.
Btw, they both work perfectly when connected to my Win10 computer…

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Just received my new SD/USB Adapter - Sandisk SDDR 121 G35 (super compact little thing! Nice!) and it booted perfectly - I didn’t even re-burn the image on the uSD card, which was created using the Kingston adapter into my Windows PC - just popped it in and it booted straight up.

Incidentally after the fact, I also tried the micro SD card in an SD Adapter in the Kingston USB Reader and that booted fine too; so is only directly in the micro slot that the problem exhibits; which kinda suggests a connection issue - however there is no issue either writing to the micro or reading it in Windows, it is only the boot recognition that seems to be a problem.

Most likely a bad contact.
Windows may have a fallback strategy for readerrors, reducing the clkspeed. I doubt the tiny bootcode of our boxes will have this, only Pass or Fail.
We had seen similar quality issues on internal cardreaders:

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