@LMCMIL 

Ethernet Backhaul: Run a direct Ethernet cable between the two routers. This is the best and most stable solution for a Mesh network.

2.    Powerline Adapters: If the apartment and garage share the same electrical meter, use these adapters to transmit the internet through your electrical outlets, bypassing thick walls.

3.    Add an Intermediate Node: Place a third Mesh device halfway between the two (e.g., near a window facing the garage) to bridge the wireless signal.

4.    Reposition Devices: Move the main router in the apartment closer to the wall or area that directly faces the garage to minimize physical obstacles.

  @waseemadiga thanks for the reply

1. cant run a cable, my apartment is on the 1st floor and the garage on the -1

2. apartment and garage share the same electrical meter but i've been reading that using a powerline has some limitations/issues, but might consider it

3. have no spot to place a 3rd mesh devise

4. the main router is already at the best position and closest possible to get the signal to the garage

  @LMCMIL 

Since the other options are out, Powerline adapters are your best practical solution. While they do have limitations, your speed requirement is very low (10-15 Mbps for a wallbox). Powerline will provide the stability you need across floors, which Wi-Fi cannot guarantee.

Additional tips you can suggest:

1.    Setup: Connect one Powerline adapter to the main router, and the other to the AX53 in the garage via Ethernet. Let the AX53 handle the Wi-Fi broadcast.

2.    MoCA Alternative: If there are existing Coaxial (TV) cables between the apartment and the garage, use MoCA adapters instead. They transmit internet through TV cables and are much more stable than Powerline.