Hi,
libqt5webview5 still depends on qtwebengine-abi-5-15-14 which is provided by virtual package libqt5webenginecore5. qtwebengine-abi-5-15-14 can't be installed anymore though because libqt5webenginecore5 was updated to version 5.15.15. This breaks eg. plasma-discover because this package depends on libqt5webview5.
Have a nice day
knappe