That totally depends on what angular resolution you require and what distance you are comfortable with. Using that list Apple's Retina concept starts at 57 and 4K 27" is ~60. And even that is assuming you place a 27" screen the same distance away from your eyes as a 24" or even 21" screen as all the iMacs use the same viewing distance.

But I'm glad we got over the idea that 220dpi is a magical number. Otherwise not even the iMac or the Apple Pro XDR displays counted as HiDPI.