Regression: camera and home keys no longer work on Positivo Mobo 5900

It was noticed that the home and camera keys on the netbook Positivo Mobo 5900 no longer work on Xubuntu 18.04. Originally, this netbook came with Ubuntu 12.04 but that version is now unsupported, so they are being upgraded to newer Ubuntu versions. Most of its functionality was recovered, but the home and camera buttons in the front of the netbook no longer work.

When used in tent mode, the only three keys available are the power button, the camera button and the home button.

I did tests with the 4.15 kernel and the camera button was working back then while I had no success with the home button.

This netbook model is one of the Classmate PC that was distributed to schools, this particular model having a gma500 GPU, being limited in graphical capabilities, thus requiring Xfce with compositing disabled to work decently. Also, its touchscreen requires evdev instead of libinput to work.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-5.0.0-37-generic 5.0.0-37.40~18.04.1
ProcVersionSignature: Ubuntu 5.0.0-37.40~18.04.1-generic 5.0.21
Uname: Linux 5.0.0-37-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
CurrentDesktop: XFCE
Date: Sat Dec 14 13:04:00 2019
InstallationDate: Installed on 2019-11-16 (28 days ago)
InstallationMedia: Xubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
SourcePackage: linux-signed-hwe
UpgradeStatus: No upgrade log present (probably fresh install)