Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
Sorry about that. It's been a while since I've done any Roku development, especially on the What's On Channel, which I wrote over 8 years ago. I assumed I'd stored the search history in the device's "Registry", which can be reset by deleting, re-booting, then re-installing the channel. However, I went back and looked at the code. The channel actually uses a system-wide search history store. I didn't implement a Clear History function, and the Roku System Settings do not offer a way to clear it.
Anyway, the system-wide search history can be deleted from any other channel that implements the Clear History function. For example, install the SHOUTcast Internet Radio Channel (https://channelstore.roku.com/details/2115/shoutcast-internet-radio), select "Search", enter something in the search box, then when the Clear Search History box appears, select it, and all your search terms (including those used by the What's On Channel) will be gone!
The app communicates with an external server to get the list of channels and program information, so no updates are required for the What's On Roku Channel itself if a TV provider changes its channel lineup.