Support for TP-link RE205 v3

Ok, so I have this setup at my home a TP-Link Archer C7 v5.0 with two TP-Link RE205 v3.0 with that I can have OneMesh network setup.

I know that OpenWrt fully support the router but there isn't post regarding of supporting the range extender (RE205 v3.0) so I can have all the setup running OpenWrt (if I change just the main router to OpenWrt firmware I would loose the Mesh network function since there is n nothing about how OneMesh works so I can reproduce it on a non-tplink firmware).

Anyways opening up the RE205 v3.0 device so I can inspect what's running, Its main SoC is a Mediatek MT7610EN and I found that a user on this forum (Compile 'kmod-mt7610e' for MT7610EN) has run OpenWrt with it, is this could be a starting point?

What could be some sort of safe option without resulting in a bricked device?

Well here is a pic of its internal:

(Moved to the For Developers section.)

Any advice?

Running an initramfs-image from RAM should be a safe option.

I tried to access the bootloader to start an OpenWrt-image, or at least to be able to recover if something went wrong.
I connected ground of my serial interface to TP5.
TP4 seems to be 3.3V
TP2 is TX (connect to RX of the serial interface)
I thought TP1 might be RX, but TP1 seems to be pulled to ground.

I can see output from the bootloader (u-boot 1.1.3). But I cannot interrupt it, I cannot send commands to the bootloader.

Did anybody had more luck than I?
Did anybody found TP3?

This is the output from the bootloader:

cid reg:00010102, cid:1[04010D07][04010D0A]
DDR Calibration DQS reg = 00008988

DDR Calibration MEMCTRL reg = 0E120003

U-Boot 1.1.3 (Nov 28 2020 - 10:44:01)

Board: Ralink APSoC DRAM:  64 MB
relocate_code Pointer at: 83fb8000
flash manufacture id: 20, device id 70 17
Warning: un-recognized chip ID, please update bootloader!
*** Warning - bad CRC, using default environment

Ralink UBoot Version:
ASIC 7628_MP (Port5<->None)
DRAM component: 512 Mbits DDR, width 16
DRAM bus: 16 bit
Total memory: 64 MBytes
Flash component: SPI Flash
Date:Nov 28 2020  Time:10:44:01
icache: sets:512, ways:4, linesz:32 ,total:65536
dcache: sets:256, ways:4, linesz:32 ,total:32768

 ##### The CPU freq = 580 MHZ ####
 estimate memory size =64 Mbytes
RESET MT7628 PHY!!!!!!

Please choose the operation:
   1: Load system code to SDRAM via TFTP.
   2: Load system code then write to Flash via TFTP.
   3: Boot system code via Flash (default).
   4: Entr boot command line interface.
   7: Load Boot Loader code then write to Flash via Serial.
   9: Load Boot Loader code then write to Flash via TFTP.
default: 3

You choosed 3

3: System Boot system code via Flash.
## Booting image at bc020000 ...
text base: 80000000
entry point: 8000c150
   Uncompressing Kernel Image ... OK
No initrd
## Transferring control to Linux (at address 8000c150) ...
## Giving linux memsize in MB, 64

Starting kernel ...