Comment 0 for bug 1880596

Opening new bug as instructed by Sebastien Bacher (seb128) in bug #1866556.
Related upstream bug: https://gitlab.gnome.org/GNOME/mutter/-/issues/1242

Reproduction with Ubuntu 20.04 on affected convertible devices like Dell XPS 9575 2-in-1:
1. Log into gnome-shell Xorg session ("Ubuntu")
2. Fold the display back, to switch to tablet mode. (On properly supported devices, this disables the physical keyboard)
3. Use touch screen to touch any text input field, including gnome-shell fields like Activities > Search
-> EXPECTED RESULT (occurred on Ubuntu 18.04 through 19.10): The OSK appears
-> ACTUAL RESULT: nothing happens, you cannot enter text
4. Swipe from bottom of screen in order to summon OSK on demand:
-> EXPECTED RESULT (occurred on Ubuntu 18.04 through 19.10): The OSK appears
-> ACTUAL RESULT: nothing happens, you cannot enter text (e.g. into text fields of foreign toolkits that are expected not to trigger the OSK automatically)

Note that the EXPECTED RESULT still happens under Wayland in 20.04. Only the Xorg session is affected by the issue described in this bug.

Also note that Accessibility was NOT necessary to be enabled in 19.10 and before. (When enabling it in 20.04, the OSK does appear under Xorg, but this should not be necessary)

(On Wayland there is a different changed behavior with the OSK not appearing in the device's laptop mode, i.e. with the physical keyboard enabled. This seems intended and a different issue as per https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/872)

This bug report was created on Dell XPS 9575 2-in-1, where the bug reproduces.
I can confirm that the EXPECTED behavior occurred under Xorg in 19.10 on this machine as well as on the Asus Zenbook Flip UX561UD, and stopped with 20.04.
It probably also worked with 19.04 and possibly 18.10, but I ran mostly Wayland and so am not entirely sure. (I never ran 18.04 on these devices)

Other hardware reported to reproduce the issue (and in part are said to have been working in 19.10 and before, down to 18.04) include:

In bug #1866556;
Lenovo ThinkPad L390 Yoga
Asus ZenBook UX370UAF
Acer Switch 11 V sw5-173 (said to have worked with 18.04)
(Possibly HP ENVY x360 15-cp0 and Lenovo ThinkPad X201 Tablet, though the tablet mode seems unsupported on these devices and so the issue might be different)

In upstream bug:
Dell Inspiron 15 700 2-in-1

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-shell 3.36.2-1ubuntu1~20.04.1
ProcVersionSignature: Ubuntu 5.4.0-31.35-generic 5.4.34
Uname: Linux 5.4.0-31-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Mon May 25 19:59:40 2020
DisplayManager: gdm3
InstallationDate: Installed on 2018-09-13 (619 days ago)
InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Alpha amd64 (20180912)
RelatedPackageVersions: mutter-common 3.36.2-1ubuntu1~20.04.1
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to focal on 2020-01-04 (141 days ago)