Hello

I've LeEco Super4 X55 TV connected to Pioneer VSX-822-K receiver through Digital Optical Audio Toslink Cable for Audio and no HDMI cables attached to the receiver.

The TV is an Android TV and i've issues controlling receiver volume with the leeco remote.

Can i use flirc plugged into tv's usb port and configure it to control receiver volume with the leeco remote?

If you want to know if Flirc is able to control your TV, connect an USB keyboard (can be either wired or wireless - but not bluetooth) and try controlling the TV with it. The keyboard should have multimedia keys - at least volume control ones, so you can check if you are able to control the volume.

As for the LeEco remote, if it's an IR remote, there's fairly big chance that would work. But both Flirc and TV will get the signal at the same time so both will control the volume at the same time which may (or not) cause some issues.