Iiyama [1], Dell [2] and LG used a 27" 5K iMac display for a little while, but as production at Apple wound down you can no longer really buy those in most places.

[1]: https://www.anandtech.com/show/12568/iiyamas-prolite-xb2779q...

[2]: https://www.dell.com/ae/business/p/dell-up2715k-monitor/pd