Hi,
The default still camera format for iOS devices has been HEIC for several years now. When printing these files to the M281fdw via iOS or MacOS, the printer receives the file instantly, makes the warmup sound, shows 'printing document' but only beings printing about 60 to 120 seconds later.
The same files converted to JPG, or photos taken with the camera format changed to JPG, print immediately.
The firmware is up to date, date code 20200612. I have tested with multiple iOS devices and Macs, and with a different router, wired and wireless.
Hopefully if someone from HP sees this post, they can replicate this issue and it can be fixed in firmware soon...