Probably not. But maybe.
Tech specs of iPhone 12 Pro says: "Video mirroring and video out support: Up to 1080p through Lightning Digital AV Adapter and Lightning to VGA Adapter (adapters sold separately)"
So get the Lightning Digital AV Adapter, connect a HDMI to USB-C adapter (such as the Club 3D CAC-1332), then see what happens (possibly nothing). This can only work with the 27MD5KL model which can accept non-Thunderbolt input (unlike the older 27MD5KA model which requires Thunderbolt conversion). However, it might not work since the UltraFine 5K's EDID doesn't include a 1080p timing. Is there an upscaler to convert 1080p to 1440p or 4K?
The iPhone and iPads that using lightning cable can't do USB and video at the same time, so you may need to attach USB (for the CAC-1332 adapter) to something else.
