Lately, when I first open to Roku main screen, "cursor" is over Home, but Roku automatically starts adding another channel app (different every time) which I don't have. I've rechecked to make sure I wasn't opening one of the ads on the right, or somehow was starting from anywhere but home.
How do you "open to Roku main screen"? If you just switch inputs on a TV or AVR, then I wouldn't expect anything like this to happen.
On the other hand, if you use HDMI-CEC for switching and you press something like OK or Play on the Roku remote, and you have one of the screen saves with ads (including the default one) then I could see this happening easily.
(One easy fix for the above, is to use one of the screen savers without ads such as the 2 clock screensavers.)
It might be related to screensaver mode. I just tried recreating different scenarios, and of course now it's only happening sporadically. (Would using play/ pause button to get out of screensaver, rather than OK button, be issue?)
But I think it occurs in other situations, e.g. switching from TV mode to HDMI1 (where Roku's plugged in).
Also, I didn't mention, it sometimes opens the Roku Channel app, in addition to other timee adding uninstalled channel apps.
The only buttons I ever use to exit the screensaver are the Home and Back buttons. Yes, hitting the Play button could trigger also one of the ads in the SS unintentionally. I'd stick with the two listed above.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
Not to mention the new ad that sometimes shows up at the bottom of the main menu that is triggered with Play/Pause. Never use that button if you're not actively watching/listening to something or otherwise inside a channel/app.