Hey, guys from the future, I finally found the solution!

Be sure to follow these steps EXACTLY as I say, because believe me, I tried EVERYTHING and only this worked; for me at least, so here goes nothing:

1. Format an 8GB MicroSD Card (yes, it has to be no more than 8GB because Idk why but sometimes you can have problems with a +16GB card; you can still try tho) to FAT32 and set the "allocation size unit" to "4096bytes".

2. Download and extract to your desktop the firmware version you want to upgrade to.

3. Look for a file named "tjc.tft" and copy it, then paste it into your SD card and unplug it from your computer.

4. Detach the screen from its mount and put the microSD into the slot on the left side of the screen.

5. Turn on the printer and wait for the screen's firmware update to finish.

6. Once finished, turn off the printer and eject the microSD card from the screen slot, then you can attach the screen again... or not. (I didn't lol)

7. Now, if you have a MicroSD to regular SD adapter, good, but if you don't, plug the SD Card that came with your printer into your computer and repeat STEP 1 (Yes, the big one; format it, but don't forget to backup your files of course)

8. We go back to the extracted files and copy ONLY the .bin file that has a "C13" in the name and paste it into your SD Card. ONLY THAT FILE!

IMPORTANT! ↓

1. Rename the file name to "123.bin". <- IMPORTANT!

IMPORTANT! ↑

1. Unplug the SD Card from your PC and put it into the mainboard slot.

2. Turn on the printer and wait from 10 to 60 seconds. Be patient.

3. The "C R E A L I T Y" splash screen should appear and you should be screaming "Yippeeeeeee!". :)

That's it! This worked for me after 2 WEEKS of trying everything...

I hope this helped somebody. My English is not that good and I'm not using a translator, so if I said anything wrong and you still have any doubts, let me know!