I successfully flashed a TL-MR6400 with LEDE snapshot.
First of all, of course I know how to setup port forwards!
It ran very good until I needed to set up port forwards for connecting remotely to my services, mostly OpenVPN and SSH, like I had before in the stock firmware.
After a massive headache I finally found that inbound connections seem to never reach the WAN interface of the device (router side, not the LTE)
This device has an integrated LTE module that runs on android and have a DHCP server...
WAN interface on LEDE is a normal DHCP client by default and connects normally, internet outgoing connections also work normally.
The problem lies on the incoming connections that seem to never reach the WAN interface of LEDE system, I could clearly see it running tcpdump on that interface (usb0=WAN)
If I run tcpdump via adb shell (it's integrated and will run directly on the LTE module firmware) I can see all inbound connections, but they seem to never be forward to the WAN ip of router
As I understand something on the LTE module side is blocking these connections, but I'm not really sure.
I had to revert to OEM firmware, port forwards work normally as before (before trying LEDE on this device).
Maybe the stock firmware make changes in the LTE firmware side (firewall rules maybe??) that LEDE is not doing?
With this post I hope other MR6400 users could give some feedback about running LEDE on these devices.
Thank you for taking the time.