Smart TVs are so user hostile now that this doesn't work for me personally anymore. Every TV I've seen recently always tries to get back to the "home" screen so they can funnel you into more ads and/or content that makes them money. If I have the TV set to the HDMI source for my connected HTPC, turn off the TV, and turn it back on again, it will be back on the TV's home screen. If I switch to an HDMI source that isn't currently outputting video it will switch back to the home screen in five seconds. I was at a friend's house over Thanksgiving and when he tried to navigate away from the home screen on his Vizio TV to a different HDMI input he got a confirmation dialog box with an ad embedded in it asking him "are you SURE you want to change inputs?" It's ridiculous.
For now I spend the extra money for "digital display" TVs that are just dumb input for HDMI devices but I fear that someday that option will either disappear or fall significantly behind regular TVs in display technology.
Try TCL. I just got a second one after 6 years with a previous model of theirs that was showing signs of death. On both this new (Google-based OS) and old one (Roku-based OS), I have done the steps I mentioned above. I wouldn't have bothered typing that up if it didn't work.
Turning a HDMI device on wakes the TV and then it automatically selects that input. I've never been to the homescreen except by choice, and even then it is completely stock. Barebones, no ads - it has no internet to get any.
2. setup a one time use wifi network with randomized SSID and password (hotspot from your phone works well)
3. connect your tv to it and update to latest software
4. delete the wifi config and reset that network (roll to new SSID and password)
5. connect an apple tv set top box and never use any of the tv features ever again