Ran through each dtb using the latest CoreELEC-Amlogic-ng.arm-9.2-nightly_20200218-Generic.img build on the Droix X3 and here are the results using both the internal NIC and an external USB NIC.
Not working - Permanent black screen on the TV.
Not working - Continual Reboots.
Not working - Continual Reboots & Corrupt boot Logo.
CoreELEC Working but with no detected network or bluetooth devices (internal or external)
(Note: Both g12a device trees boot the initial partition formating screen and once complete require a hardware reboot before loading CoreELEC. The sm1 device trees do not require this extra step.)
This thread is not monitored for help and support, tou can not just try any device tree and hope for the best, the key is in the naming of them.
Based on the spec of the box the correct device tree is sm1_s905x3_4g.
If network is not working then it needs to be brought to our attention in a more appropriate thread, ie nightlies, you also haven’t said whether this is just wireless or wired or both that isn’t working.
As you have tried an external NIC as well it could be that the driver is missing but again these are all separate issues that need raising.