I'm suffering with underscan on a 1440p monitor while using an intel MBA (2015). The mini-DP port would only work with a VGA adaptor & the 1080p resolution ends up with a vertical black bar on the left as a result of the underscan.

No way to fix this either since macOS Monterey doesn't have any settings to change, ends up showing that a 40" HDTV is plugged in when it's just a 27" 1440p display...