Thanks for the reply. As regards testing different skins, I tried all that was available to no success. The Joggler is my favourite skin (on Raspberry official 7″ screen), but on Full-HD TV it displayed in about a quarter of the screen. It did not stretch to 1920xx1080. Looking at Joggler’s lua code it seems it should expand to full-hd but it did not in my environment. However I succeeded in tweaking Joggler lua code to me needs and it works ok now with my Full HD screen. I also had to enlarge fonts and improve layout in several places.
So as for now the problem is solved as for me. I suppose that the problem may return when I upgrade my TV to 4K model. And then I may not be able to tweak skin as it would involve developing resized (upsized) buttons‘ images etc.
Thanks for suggesting slimdevices forums. I found some of them online and maybe I will make use of them.