If you are considering upscaling non 4k content to 4k. Then best to leave the upscaling job to the TV. Every tv has its own algorithm to upscale. Which is designed for that particular panel. So just leave the avr to pass through the video content and not upscale anything
I have the Denon AVR2400 bought few months back, while selecting/buying the AVR, I was very particular on up scaling and later realized its not making much of a change if you are having good 4k TV. Also, mostly i watch the HD channels in Tatasky+. So, in my opinion 4k up scaling feature in AVR could be a added advantage than essential.
As others have said, if you already have a (decent) 4K TV, it shouldn't matter whether your receiver has 4K upscaling or not. Flat panel TVs are fixed pixel displays, i.e., they display everything at THEIR native resolution (4K in your case) irrespective of what you feed it. And TV scalers are fine these days. So my suggestion: save your money (on the non-4K upscaling AVR) and spend it on better speakers!