CH340G on Linux (GENTOO, vanilla kernel 4.12.3)

Hi,

I am currently struggling to get an CH340G based USB<=>serial adaptor to work on
my GENTOO Linux with kernel 4.12.3 (vanilla) and a MEGA256 MINI PRO (clone).
At the moment it acts like a perfect isolator in both direction with a nice LED
shining…

The CH340G is recognized by the CH341 kernel module correctly and a device is created
for it (/dev/ttyUSBn). I flashed a bootloader via buspirate on the board (via IDE “burn bootloader”).

Short question:
Is it simply a desperate hope to get this combo working or should I try even harder?

Cheers,
mcc01