So I recently bought a Dell Inspiron 24-5459 All-In-One for personal use. However, when I work from home with my work laptop, I'd love to be able to use the AIO as a second monitor. Is this functionality possible using HDMI? Thanks in advance for the help!
Not with the as-shipped hardware, no. You would need to add a USB video capture device of some sort - and be advised all of these introduce a lag in the signal -- you won't get the same real-time display you would on a monitor. You may be OK with that for office work but it won't be satisfactory for gaming or video use.
There is an HDMI in that I connected to, but nothing happened automatically and I can't find anything in the settings to set the AIO into 'display mode'. I'm hoping somebody here knows what settings to adjust or if it's even possible.