UP2720Q, 10-bit output on macOS?

The UP2720Q is a 10-bit monitor, supporting 10-bit color through its Thunderbolt 3 connection.

macOS has supported 10-bit color output for quite a few years now.

My setup is:

2017 15" MacBook Pro with Radeon Pro 560 GPU → Thunderbolt 3 cable → UP2720Q

Laptop is used with lid closed and UP2720Q as the only display. macOS version is 10.14.6.

As far as I am aware, all components should support 10-bit color. Yet System Information reports the monitor framebuffer depth as 24 bit = 8 bit per color:

I'm not seeing a macOS driver for this model in Dell's database. This FAQ from 2016 suggests I can only have 10-bit color in Windows, but that seems rather silly to me, at least in 2021.

What do I have to do to get 10-bit color out of this monitor in macOS?