dear friends, I noticed you almost know everything so I seek for your help as my local group couldn't help me 
drone: SMART 35 hd
FC: GEP-F411-35A AIO                               betaflight v 4.3.1
radio: TX16s with internal ELRS                    v 2.5.1      EdgeTX v 2.6.0
reciever: HappyModel ELRS 2.4 GHz EP1       v 2.5.1

I bought used SMART 35 without reciever, soldered ELRS to UART 2 (as FC demanded). It didn't work (solid green light problem). I swapped it with vista on UART 1 and it worked. I flashed it, flashed TX16s internal ELRS, binded them - telemetry works. 
I set MIXES to AETR (radio and BF), set internal module to CRSF - external off, changed ports for RX in BF, set Serial and CRSF in Receiver tab.
But still I get no response in BF from sticks movement in Receiver tab, like it didn't see my radio.

The led light on Rx is solid green. On FC there is solid red and blinking blue lights. 
Pls help me 

diff and dump from CLI

  diff i dump.txt (Size: 30.53 KB / Downloads: 86)

I believe your issue is the same in the one described in the thread linked to below. In a nutshell there seems to be an issue getting an ELRS receiver working on UART1 of the GEP-F411-35A AIO FC. The solution is to wire it to UART2 instead.

https://intofpv.com/t-elrs-ep1-receiver-troubleshooting

Maybe I didn't explain it correctly. At the begginig I soldered recevier (GND, VCC, TX, RX) to UART 2 because FC scheme demanded me to do it (as in photo below). But for me it didn't work at all, I couldn't bind it or flash it. On UART 1 there was Caddx Vista. I swapped them and now the recevier is on UART 1 and it works well (at least works better) because I could flash it and bind with TX16s. 
at the link you provided https://intofpv.com/t-elrs-ep1-receiver-troubleshooting they swap from UART 1 to UART 2. That's what I already had at the beggining and it will not work for me.

If you are getting a green LED on the ELRS receiver then the receiver is bound to the module / transmitter so the problem is likely to do with the Betaflight settings or a hardware issue with the FC. All of your Betaflight settings look correct so that point the finger at the latter.

That particular GPERC FC appears to be problematic with an ELRS receiver and the other member might have just got lucky with getting UART2 to work. Different batches of the same FC mught have components on which have slightly different tolerances and may be the reason that neither of your UARTs appear to work.

If you still aren't seeing stick movements in Betaflight then first check the CHANNEL MONITOR page on the screen of your transmitter to see if the bars on that are moving when you move any of the sticks. If yes, do you have another different FC that you can try the ELRS receiver on to confirm if the receiver itself is actually working or not? If you do then I would try that next. Once you have confirmed the receiver is actually working you can try adding a 300Ω-1kΩ resistor between the RX input on the FC and a 3.3V pad as shown HERE to see if that fixes the issue.

I checked channel monitor page (MIXES tab) and I see stick movements when I move them one by one. I don't have another different FC so I can't confirm if the receiver is working Nevertheless I added 750 Ohm resistor between the RX input on the FC and a 3.3V pad ... but it didn't help or I didn't do something properly (check photos BEFORE and AFTER)




I wonder if it matters that Vista SBUS is still connected to RT2? I tried to disconnect it, without any effect. 


maybe I should try to flash receiver and radio internal modul once again? I'm not sure anymore which option should I have enabled (Compatibility Options / RCVR_INVERT_TX ?)


I checked CLI and I have:

# get serialrx

serialrx_provider = CRSF
Allowed values: SPEK1024, SPEK2048, SBUS, SUMD, SUMH, XB-B, XB-B-RJ01, IBUS, JETIEXBUS, CRSF, SRXL, CUSTOM, FPORT, SRXL2, GHST
Default value: SBUS

serialrx_inverted = OFF
Allowed values: OFF, ON

serialrx_halfduplex = OFF
Allowed values: OFF, ON

The RCVR_INVERT_TX is for use when connecting an ELRS receiver to an SBUS pad (the RT2 pad on that particular FC). You are using the R1 pad you you need to untick that RCVR_INVERT_TX option before you flash ELRS firmware to the receiver. So if you have that switched on, make sure it is switched off and re-flash ELRS firmware to the receiver.

The serialrx_inverted CLI setting only applies when SBUS is selected as the serial provider so that setting is irrelevant for CRSF.

If changing the RCVR_INVERT_TX option doesn't fix tour issue then I'm unfortunately out of ideas unless you have a faulty receiver or that FC just doesn't want to play ball with an ELRS receiver. You either need to try that receiver on different FC (not a GEPRC one) or you need to try a different known working ELRS receiver on that GEPRC FC. Then you can confirm if that current ELRS receiver itself is the cause of the issue, or not.

I flashed again my TX16s internal module and EP1 receiver with this RCVR_INVERT_TX turned OFF .. and you know what? it worked!! that was the issue all the time I guess, this option is enabled by deafult and I left it this way (my bad).
Thank you for your time and help you provided, problem solved !!

No problem.

Happy flying

Thanks! It solved it for me too!