This bug has been copied from bug #1632904 and has been proposed to be backported to 7.7 z-stream (EUS).
I tested gnome-settings-daemon-3.28.1-5.el7 on RHEL7.7z and was able to verify the OSK operates as expected, including GTK apps like gedit, terminal etc.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.