I usually recommend against this particularly if you intend to have the display or camera kept on.

The issue is that modern mobile devices cannot bypass the battery.

This means that when the device draws power it does so from the battery, even if the battery is fully charged and the charger is plugged in.

In that case the device will draw from the battery and the charger will top up the battery. This process, particularly with higher draw or increased heat from the display/camera/etc will cause the battery to wear at a much higher rate than normal use.

If left unchecked in this scenario for long enough this can become a fire hazard as the battery will eventually pillow or puff up. When this happens it makes it very easy to cause a short that will result in a fire. This can even happen on its own if the battery pillowing damages the screen or some other sharp component that then punctures the battery.

Virtually all mobile devices you can still get your hands on will be vulnerable to this issue unless you open them up, remove the battery, and then solder/wire a bypass. There is no way to bypass this behavior in software. Even with the battery bypassed you may experience issues with some devices refusing to boot in that configuration.

For that reason it’s generally a better decision to get an SBC or an old laptop/mini-pc instead and if your needs call for it: a touchscreen to go along with it.

Laptops are typically not as susceptible to this. Many relatively new laptops still had removable batteries and will therefore generally work with the battery removed and only a charger attached.

And of course this is not an issue that will occur overnight.

If you want to use a phone temporarily as a touch panel/camera/server then by all means go for it! But I would suggest finding a safer solution if you intend something long-term as any mobile device will eventually become a fire hazard