Is that really a problem that happens because a TV is "smart" or not? I'm using a LG 4K OLED TV, connected to the internet with a bunch of apps (so smart) and it's ready to be used in like 2-3 seconds after I power it on. Are other TVs really that much worse? I only have experience with LG ones, so I might just be lucky here.
stayed in an airbnb once where the TV would take ~15 seconds to be ready to control, of that time, about 5 seconds was already playing content but you couldn't control the volume. I don't remember the brand, but it wasn't some unknown thing.