TL;DR

Using an external portable AOC 16T2 monitor as a secondary screen works well on a Ubuntu laptop, but it needs a bit of tweaking.

xinput map-to-output 14 HDMI-A-0

Connecting a touchscreen to an Ubuntu Laptop

One of the first things you’ll do when connecting an USB device, getting info about the device. Is it recognized? Issue an lsusb before and after connecting the device and watch the difference. In this case:

Check connected USB-devices in Linux

lsusb
Bus 001 Device 011: ID 1fd2:9004 Melfas LGDisplay Incell Touch

So Ubuntu does recognize the AOC 16T2 monitor as a touch-device.

For that of course an USB-C (3.0) display cable is necessary, touch information is not transferred over an HDMI cable, in that case you’ll need another USB-C cable, a USB-C 2.0 version is sufficiant.

Another check if the screen is recognized as a touchscreen, issue the xinput command, before and after

Check input devices in Linux

xinput
Melfas LGDisplay Incell Touch id=14 [slave pointer (2)]

Check connected screens in Linux

To check screen use xrandr.

xrandr
HDMI-A-0 connected

Using a touchscreen on Ubuntu, and using a touchpad at the same time causes some confusion. At the moment you use the touchscreen your mouse disappears. That does make some sense, otherwise you feel urged to move the mouse, which is of course not needed on a touchscreen.

Tip: enable locate pointer when using touchscreen

Enable the locate pointer settting in the accessibilty settings, helps you to find you’re invisible mouse. Press CTRL and you can find your mouse-position again.

Once you’re used to that, an external touchscreen works rather strange out of the box, when you’re using join display, extended desktop as a default for attaching an external monitor, which is wanted in most cases.

Strange default in Ubuntu using secondary touchscreen.

Visual the desktop is extended, but for touch-input it is not. SO the visual-desktop is different than the (touch) input-desktop. That means when you click on the second monitor, the gesture is interpreted like you touch on the first monitor.

And I tried but this cannot be solved by changing the order of screens in the display-setting, moving the external monitor to the left.

To get it working you’ll need to issue a command in the terminal.

Making a external touchscreen working in Ubuntu

To map the touch.input-desktop to the visual-desktop:

xinput map-to-output 14 HDMI-A-0

This will map the touch-desktop to the secondary AOC touchscreen.

You do wonder why this is not the default in Ubuntu. I’m not sure, maybe it was in earlier days.

But this is not working in Wayland

And there is a bigger problem. This solution works only in X11 window server, not in the new Wayland environment, which is the default nowadays in nearly all modern Linux desktop, including Ubuntu 22.04 LTS.

As it seems xinput does not find your touchscreen annymore, so no mapping can be done.

Wayland does recognize the touchscreen, there is no option yet to map  it to the right screen.

That is plain stupid a pity.

So that means you have to logout/login and switch to X11 to use your external touchscreen.

Hopefully this will fixed soon.

Maybe you have seen this message more often then before, while updating your computer manually through the terminal:

The following packages have been kept back:
<package-name>
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.

Historically that could be the case with the classic commands

sudo apt update && sudo apt upgrade

Because that command is careful (doesn’t update) about packages that can introduce dependency conflicts

But that update command has been superseded by

sudo apt update && sudo apt full-upgrade -y

The latter commands also remove packages to resolve dependency conflicts, and in most cases that is everything you want.

But now upgraded to Ubuntu 22.04 I see the kept back message more and more, even when I did a sudo apt update && sudo apt full-upgrade -y

And as it seems, that is absolutely OK, it’s part of the new phased roll-out mechanism. Packages that can break things are introduced in batches. First only a small percentage of users are getting the new version, so if there are bugs, only a small number of people are hit, and the bugs can be fixed before it is introduced on a bigger scale.

How to check if packages are `phased`

apt-cache policy <package-name>

e.g. gnome-remote-desktop

apt-cache policy gnome-remote-desktop 
gnome-remote-desktop:
Installed: 42.4-0ubuntu1
Candidate: 42.7-0ubuntu1
Version table:
42.7-0ubuntu1 500 (phased 0%)
500 http://nl.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
*** 42.4-0ubuntu1 100
100 /var/lib/dpkg/status
42.0-4ubuntu1 500
500 http://nl.archive.ubuntu.com/ubuntu jammy/main amd64 Packages

Just be a little patient. The update will normally come in a few days.