/usr/lib/mono/accessibility/UIAutomationClient.dll is in libmono-uia3.0-cil 2.1-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/accessibility/../gac/UIAutomationClient/3.0.0.0__31bf3856ad364e35/UIAutomationClient.dll