Flashing Mercusys MR70X v1.0 - v1.8-br

I bought a MERCUSYS MR70X v1 router.

It turns out that the label on the bottom of the router says: BR/v1.8 - Brazilian Version
but on the configuration page, it says:
Firmware Version:
1.0.11 Build 20230921 Rel. 70402(4252)
Hardware Version:
MR70X v1.0

It seems that the hardware is v1.0, but the firmware is natively v1.8-br.
It doesn't allow me to downgrade to previous versions. Can anyone help me with a solution to install OpenWrt on this router?

Support for mr70x is still very new and it still seems to have rough edges according to recent forum posts:
Several people had it bricked just recently or had failed to revert back to stock, with not yet fully analyzed and resolved cause.

There is no beginner-friendly wiki page yet and the discussion threads are still ongoing. You need to rely on the commit message for installation instructions in the mean time: https://github.com/openwrt/openwrt/pull/12104

I would study the threads first and avoid experiments. It you have trouble following the tech discussion in those threads or fear resetting a bricked device via serial cable, I would advise, to probably wait for 2-4 months, until those issues got sorted out.

I tried to do what the forum says, but I was not successful. I would like to know the procedure for flashing via serial. This router is for testing, so it's okay if it gets bricked in the process