[wrxtasy]

So I'm thinking mecool km3/km9 + usb ethernet, or is not the way? And there is proven box with 1gbe?

At the moment S905X2 devices are likely to get better - reasonably stable - firmware support vs the shiny new S905X3 that is using a new AML Linux Kernel.

Suggestion, find the most popular hardware threads on the CoreELEC forums and find a device that has Gigabit LAN and see how users are going with them.

It's simply too hard keeping up with all the different, highly varied Cheap China boxes for running CE Kodi, and if they do work properly or not.
You need to do some self reading over on the CE forums to remain right up to date with the best cheap choices:
https://discourse.coreelec.org/

That is the reason people buy proven hardware for CE Kodi - ie. the HardKernel ODROID N2, the Ugoos AM6 and the X2 Cube, the Khadas VIM linup.
We know they work, with all the exact same Hardware specs in each box and most have Gigabit LAN.

I would like to avoid anything that runs out of the sdcard (odroid).

There are numerous options for running CE Kodi on the 2019 Chipset Android devices - you can boot from USB3 flash drives for example - and in the case of the N2 - a pluggable eMMC flash storage module.

EDIT Speaking of USB3 Flash Drives the following article is worth a read. For CE Kodi you want superior - Small file - R/W speeds:

Wirecutter - The Best USB 3.0 Flash Drives (click)

W.