It is not the bug. Apple make this on purpose and there will be no fix. You have to buy 4k monitor

Apple answer to you - buy 4k monitor

Which monitor do you have?

It's not an issue for Apple. Don't wait "fix" - it will never be "fixed" because apple intentionally limits hidpi for monitors less than 4k. The only solution for you - buy a new 4k monitor

Probably will not work with your ultrawide monitor. Apple does support "classic" 4k monitors(it could be any vendor). But im not sure if it supports ultrawide monitors... i think no