Mercku M2 mesh hardware

Hi,
My new canadian cheap-ISP (IVCTel) provided me a mesh router of an uncommon brand: Mercku, a recent Toronto-based startup.

The specs looks ok for the price, notably a 1GB flash storage (it seems quite large for a router).
Specs here: https://shop-ca.mercku.com/products/mercku-hive-mesh-wifi-system
Even the bee (mesh-relays) are supposed to each have 1GHZ/128M/1GB for $60 !?

From the firmware they provide online (https://www.mercku.com/support/download/) it seems to be linux-based (the firmware contains some openwrt function!?) and that TFTP install is possible.
Weirdly, the router (web-interface/wifi-name) is branded for another Canadian ISP (CIKTel) so there might be a custom firmware for each company.

Do you think it would be safe to replace it with openwrt (and possibly return to the stock firmware).
I wouldn't risk to brick the router as it is rented by the ISP.
I am a noob at embedded systems, so I am wondering what is the best way to reverse engineer the firmware (like find the wifi chipset model, ...). I ran binwalk on the firmware, it looks like binary are for MIPS.

Thanks for your advices and opinion on the hardware!