Hello, You want to run Linux exclusively, no Android? Is that right?
As to flashing firmware, while certainly there is always some risk when flashing firmware, it is pretty low. Flashing firmware is not too difficult. I would be happy to assist you if you want to try it. It will involve a PC, the Amlogic USB Burning Tool(free Windows program), and the supplied USB-to-USB-C cable.
If your VIM2 is booting to Android now, M mode is likely unnecessary in this instance.
Photo linked in the post above is of VIM, the VIM2 is slightly different with regards to M mode contacts. Here is photo of VIM2…
Khadas offers standalone Linux Ubuntu, and a dual-boot versions with Android and the Linux.
Additionally, @balbes150 offers many Linux variants, many of which can be booted and ran from from SD card, or installed to the eMMC. Server and desktop types are available.
Guides for many needs can be found on Khadas Docs.