Using I-device as a computer monitor

According to various people posting articles and YouTube videos online, it's possible to use most any Apple I-device, new or old, as a wired computer monitor.

The idea seems to be that you plug an HDMI cable into a newer computer that has an HDMI monitor output, and the other end into something called a "HDMI capture card" that has a female HDMI connection and a male USB-A connection. The capture card is in turn plugged into an adapter going from Lightning male to USB-A female. It is then possible to use one of several I-device "apps" to view the video monitor output from the computer, without having to install any special software on the computer.

At least that's the idea.

After getting a "capture card" (a model that was specifically recommended by at least one presenter), and plugging it into each device via a Lightning to USB adapter (which works fine for things like USB audio interfaces, which are instantly recognized by the iOS system), I can't find a way to make any "app" I've tried to see the connection. In testing with my laptop that has an HDMI output, when all is connected the computer can see the monitor connection and attempt to use it, and on plugging the "capture card" directly into another computer, I was easily able to use VLC Player on that computer to view the video capture from the HDMI-equipped laptop.

I-phone "apps" I've tried include:

"USB Camera to NDI"

"HDMI"

"Imaging Edge Mobile"

"Monitor+"

"Reflections OTG"

"OBS Camera Studio HD"

"USB Camera pro-captureinskam"

"V-SCOPE"

"CamX - USB Camera"

"Endoscope Pro"

"Smart Endoscope"

"UVCPlayer"

"Splashtop Wired XDisplay"

"Duet Display" (has additional complications regarding signing into an extra account, which seems just unnecessary)

I have yet to get any of these to see the HDMI capture connection. Some wanted to look for a network or Bluetooth connection, some appear to be intended for a specific and very limited list of HDMI devices, while others seemed to want a direct computer connection with a special program installed on the computer (something I'm trying to avoid). All insisted that nothing was connected - despite several of the programs being specifically recommended for this use.

Since the iPad typically complains that it is not compatible with the accessories when I plug in the adapters, I am wondering, is there some particular reason neither of these devices would be able to see the HDMI capture output? I found one or two resources talking about turning on something called "OTG" or something like that, but I can't find such an option anywhere in the iOS Settings menu. (Related: is the Mini somehow specifically configured with lesser functionality compared to the regular iPhone 12? If so, is there a way to change this?)

Let me clarify again that the idea is to get the video display signal FROM a computer TO an iPhone or iPad, not the other way around.

(And yes, I know that users on this message board are NOT official Apple tech support. I'm specifically hoping to hear from other Apple device users who may have attempted this procedure and found out something about what works and what doesn't.)