The Acer Nitro XV273K can run 4K, 144Hz, and HDR simultaneously without any compression. This is achieved by connecting the monitor via two DisplayPort 1.4 cables/ports.
However, this way, the FreeSync range is limited to 48-120Hz at 4K due to the limitations of the bandwidth provided by a single DisplayPort 1.4. You can still use FreeSync with a 48-144Hz range at 1440p though!
Lastly, it’s been confirmed that you cannot simultaneously use response time overdrive and AMD FreeSync, so some minor ghosting is visible at higher frame rates.