If that was my room I’d think very carefully about large panels, e.g. Magnepan as they are fairly narrow and perfectly happy hard against a side wall. If the width is acceptable maybe Quads would be an option too, though Maggies would be less obtrusive. I’d be positioning them as semi-room dividers between the lounge and diner areas about where you have the ‘15m’ written and on the wall opposite. They should fill the whole space with sound as it comes out the back just as loud as out of the front. You’d obviously need to rotate the seating in the lounge to face them, but I can’t think of anything else that would theoretically work better in such an uneven space.