Every big UK company I have worked for doesn’t own its building. They will typically agree to rent a building for 5-20 years at a fixed rate (longer times if its being purpose built for them) .
So I would expect this is paying out the rest of the rental agreements for a building to escape the building lease.
It is to do with financial reporting and the way asset and operational costs are reported.
QT is a cross platform UI development framework, its goal is to look native to the platform it operates on. This video from 2014 explains its benefits over GTK.
Most GTK advocates will argue QT is developed by Trolltech and isn’t GPL licensed so could go closed source! This argument seems to ignore open source projects use the Open Source releases of QT and if Trolltech did close source then the last open source would be maintained (much like GTK).
Personally I would avoid Flutter on the grounds its a Google owned library and Google have the attention span of a toddler.
Not helping that assessment is Google let go of the Fuschia team (which Flutter was being developed for) and seems to have let go a lot of Fuschia developers.
Personally I hate web frontends as local applications. They integrate poorly on the desktop and often the JS engine has weird memory leaks