Sergey Lepeshkin

@Ducdanh Nguyen, if you mean usb<->uart converter, virtually anything with cmos/ttl 3.3v. i/o levels (5v. probably is fine too) will work. Based on ch340 or pl2303 or cp2101 or some FTDI chips - all they should work. But don't use usb<->rs232 converters or COM port directly.
 
If you talking about soldering some sort of connector to tv box board, then I can't suggest anything, except some straight separate pin. This test points are just separate pads and they don't suit any of connectors I familiar with. IMO better way is to solder thin flexible wires (preferably in PTFE or silicone insulation) to the board, and then solder any kind of connector to them.
 
You need uart connected only if you wish to interact by it means with tv box. Through uart you can interact with u-boot bootloader, inspect kernel output and have access to shell console with 'su' enabled. But, just to simply boot tv box, you don't need uart.

@Ducdanh Nguyen, about uart: just find someone with soldering skills - it's deal of 3 minutes to solder 3 wires.
 
Screenshots: all them taken from one tv box. I've found recovery menu only once - when accidentally flashed update.zip with system and vendor partitions taken from other tv box (also HiSilicon-based). After flashing, something went wrong while starting Android, and box automatically rebooted to recovery.

@Ducdanh Nguyen, I don't understand how you could use electrical (insulation?) tape to connect to test points... Nevertheless, all you need is a good electrical contact between wires and test points. Means has no matter. Beware: signal levels is 3.3V. Do not connect directly to RS232 interface!
 
What about flashing my modified update.zip - don't worry. It doesn't alter partition table, bootloader and backup partition. If something goes wrong, or you just want original firmware back - just connect power while holding button near "A/V" jack. This will start reflashing using your original update.zip, located in backup partition. 
 
If you want to extract your original update.zip from backup partition, simplest way to do this is using uart. Connect uart to pc, boot tv box normally, open serial port on pc (115200/8/n/1), issue 'su' command, mount /backup and copy /backup/update.zip anywhere you want.
 
About laptop - I don't understand, how it's related to this discussion... If you want to compile armbian using it - go ahead. It doesn't matter what cpu architecture or type of memory it uses. All you need is correct toolchain, which suits our tv box SoC. 

If someone interested on this tv box: I've managed to download original firmware image (update.zip) from backup partition.
Also I cleaned it from malware (at least I think so) and packed as modified update.zip.
Files are located here: https://drive.google.com/drive/folders/1etPmH8ZG4UtPHI3Vf1U9MUHl5_gK_s-E
Further info available here (in Russian): https://4pda.to/forum/index.php?showtopic=1016510&view=findpost&p=139209499

No, he's problem is much more simpler. He have JTAG and UART wired on his board, so it's not a problem to do virtually anything with his box.
 
Are you sure? Have you successfully connected adb on PC to this tv box using usb cable?