RE: Will an AC511 sound bar fit on a U2412M monitor?
No. The AC511 is designed to be attached to the bottom facing soundbar brackets. The U2412M User's Guide shows us that this monitor has the rear facing soundbar brackets, page 7 and also the DC power connector for soundbar, page 9. Page 23 shows us that the approved soundbars are the AX510 and AX510PA (power adapter).