HDR support for non-4K resolutions?

you need hdr for 4k output

Actually, you don't.

Uhd and hdr are required for 4k output

You need UHD, in the sense that you need the TV to support 3840 x 2160 resolution, but you don't need HDR enabled to reach 4K. UHD 4K is the amount of screen resolution available measured in pixels, HDR is the ability of the TV or monitor to display more
natural colours.

Note that the Xbox One S can do HDR in games that support such a feature, but regardless of what resolution you set, all games max out at 1080P internally. If the display is 4K, it will remain in 4K, but games will only be upscaled. Only the Xbox One X
can play Enhanced titles in 4K natively.

You should be able to disable HDR, how you disable it depends entirely on your TV. Disabling HDR via the TV settings should not disable 4K screen resolution. Indeed, some Xbox One games do not support HDR, Fallout 4 on the One X can play in 4K for instance,
but it does not support (or indeed have an option for) HDR.

On my Sony Bravia Android based TV, I had to go to the main settings and enable HDR functionality. Even then, I had to set the HDR setting to 'Auto' on the HDMI port I have my console connected to. If you have HDR set to 'On' all of the time, non HDR games
will display the wrong colours, look oversaturated. With 'Auto' enabled, HDR will only operate when it detects an HDR supported game. This may not be a feature of your display however.

What make and model is your TV?

What is the model of your TV? Sometimes, manufacturers disable 4K resolution over one or more of the HDMI inputs, and you must manually enable it in the TV's settings with your remote.

The Xbox One can support almost any TV with an HDMI input. The 8/10-bits on panels only indicates whether the TV supports HDR or not, which is an optional feature. The Xbox One X can support 8-bit 4K displays (considered non-HDR
4K).

If your TV is an 8-bit panel (non-HDR), then make sure the "Color depth" setting is set to "24 bits per pixel (8-bit)" while switching to 4K UHD resolution. You may also want to experiment with the advanced video settings if you
are still having issues in trying to get your Xbox One X to display in 4K.

As far as I can tell it does not specifically state that HDR10 is required just to set the 4k resolution (just that it is required for HDR), that wouldn't even make sense. HDR10 is not required for something to display content in a specific resolution, the
resolution 3840x2160 doesn't require HDR to work, resolution is independent of HDR.

And I already know that my TV doesn't support HDR or at least doesn't support the HDR10 protocol, but that is fine, I don't care about HDR, but I do care about running things in the 3840x2160 resolution at 60Hz (which my TV definitely supports). If this
is the case MS has made a device that only works with like 10 models of TV's... why are they even selling this?

Seems to me like either a bug or an arbitrary restriction put in place to make people go spend $1500-$5000 on a brand new 2016 OLED TV supporting HDR10. I see no legitimate technical reason that the resolution can't be set to 4k without HDR. Even 4k blu-rays
with HDR do not require the TV to have HDR, it just shows the film minus the HDR details when played on a non-HDR TV.

This is what I like to call total hog wash and MS needs to fix it.

Hi,

Not all TV's support HDR on all HDMI connections.

On my Sony Bravia 4K TV, only two out of the four support HDR even though they all support 4K resolution.

What TV do you have?

You'll still get the true 4K resolution in the games, but you won't get HDR as your TV only supports up to 8-bit color.

HDR is just an additional feature on top of 4K. If you want HDR, you'll need to find a new 4K TV that supports the HDR10 media profile. Otherwise, you'll be fine with your current 4K set.