Unfortunately you wont get the YTTV app back until the dispute between Roku and Google is resolved.
In the meantime, you use YT to access YTTV: Open YT, select "YouTube TV" in the lower left corner of the UI
If you have trouble opening YT, try the list, especially options #3 and #4.
Known solutions/workarounds for YT not loading/closing to Home:
1) Check for updates: Settings/System/System update/Check now - try again
2) Restart Roku: Settings/System/System restart/Restart - try again
3) Change your Theme to the Roku Default: Settings/Theme/Restore default theme - try again
4) Change your Screensaver to a Roku clock: Settings/Theme/Screensavers - try again
5) Remove SD card (if installed) - try again
6) Remove app, RESTART ROKU: Settings/System/System restart/Restart, Add app - try again
7) Network connection reset: Settings/System/Advanced system settings/Network connection reset - try again
😎 Completely unplug power from Roku for 10-15 minutes - try again
9) Factory reset: Settings/System/Advanced system settings/Factory reset <--- last resort
NOTE for #6: Do not remove the YouTube TV app - you will not get the app back until the end of the dispute