About as bad as my room where I have two recliners where you have the sofa. 

For surrounds I mounted two Era-100s on a bookcase stuck in the corner, angled out along the walls. Far from perfect but it sounds pretty decent anyway.

Looking at your spot I'd use wall mounts, about 3 to 4 feet out from the corner. Try various angles to see what sounds best.

KEEP them at least 3 feet apart, more wouldn't hurt, to avoid them interfacing with each other's Wi-Fi connection to your router and to the soundbar.

For the front an Arc Ultra, it has the sound power to fill that room. The lack of side walls and ceiling height will impact the sound but it will still be pretty decent.

A full Sub would likely be a good addition, maybe under the TV where I have mine or under/behind d the couch for maximum impact when seated. The door corner or the corner by the dining area are also likely to work. Put it on an extension cord and try anywhere it fits.

Your room is difficult puzzle. However, I agree with ​@Stanley_4 that wall mounting Era 100’s (the yellow circles) is the best option. Sanus offers tilt/swivel mounts shown here. The Green rectangle represents an Arc Ultra. A Sub 4 might be placed under the Era 100 in the lower left. Of course, one can experiment with sub placement for best effect.