GT KING - unable to boot

[mariosbbs]

Hello, I've tried many times to at least have the pleasure of finally being able to boot from a sd card (using multiple versions released in recent weeks).
I then followed the instructions given under these releases step by step. But it was all in vain.
I created these SD CARDs using Mint Linux (latest stable 64-bit version).
Considerations:

1. any version of Coreelec 'miraculously' boots every time. Just download it and put it on any SD CARD (I have also used very old and slow 4gb SD CARDS), never any problems (at least not with regard to booting the operating system)
2. I have also tried EMUELEC and no problem
3. I also tried many times with BATOCERA and nothing to do
4. With Libreelec I wasted a lot of time and finally managed to find a way (it won't boot unless you use the reset button and you have to release it as soon as the first black screen appears... then you can reboot as many times as you like, but only until you turn on the GT KING without the SD CARD, because it's as if something is reset and when you insert it again it's ignored. You have to turn it on again with the reset button pressed )

Now some questions:

1. Why does Coreelec always boot from MicroSD without any problems? At this point I suspect they have found the right way but they consider it a secret!? If Coreelec always boots without problems, I don't understand why (apart from Emuelec) in all other cases we waste entire days without getting anything (and wondering "is the problem with the TF adapter I used? Could it be the fault of the union of the two parts that didn't go well? Am I stupid? That after over 25 years of experience with Linux I'm not capable of doing anything? Maybe it's because of something I should have known, maybe something I should have read somewhere but what isn't explained here?" and so a lot more time is wasted looking for "a clue that can help solve the problem" )

2. For the same reason, I don't understand why, for example, instead of releasing the complete image ready to insert into the SD CARD, they release it in two parts which then have to be merged (??).

I can't understand why, since I just have to download two parts as they are and join them.
The reason for all this however is the fact that I just got the GT KING to use Linux and not a Linux system whose purpose and enormous limitation is to be tailor-made to run Kodi (and I certainly don't care about that either hateful hybrid Beelink version of Android. In cases where Android is needed - with the various DRMs etc. - I use two Nvidia Shield Pro).
Is there an image already created/surely working for GT KING that can be inserted into an SD?
I still have a few days to return the GT KING to Amazon, what can I get to replace it and finally easily install / try these distros?
Thanks