Error while loading shared libraries: libQt5WebEngineWidgets.so.5: cannot open shared object file: No such file or directory
Solution 1:
You have to install the package which provides the libQt5WebEngineWidgets.so.5 file by
sudo apt-add-repository universe
sudo apt-get update
sudo apt-get install libqt5webenginewidgets5
and then retry launching application.
But the libQt5QmlModels is not available for 20.04 LTS, right. You have to ask Mail.ru to make their great app compatible with LTS version. Or upgrade to Ubuntu 21.04 only to get this application to work.