I had a trial for Topic streaming service quite a while ago. I tried deleting the channel now that the service is no longer available, but the option isn't available in the * menu.
I've seen other reports of inability to remove now-defunct channel apps.
I don't know if this will help, but you might try to remove the channel via the Roku Remote app on an Android or iOS mobile device. At the bottom of the app's Home screen, click Search and do a search for the installed channel name. On the resulting screen you should get options to Launch the channel on your Roku, or Remove the channel.
It's not available in the store, so the channel doesn't show up anywhere.
Sorry, I didn't notice that the channel tile says "Topic on The Roku Channel".
Only thing I can think to try would be to remove and reinstall The Roku Channel itself, to see if it gets an updated list of included channels.
Since you appear to have several subscriptions through The Roku Channel, you may not be able to remove it except through the Roku Remote app method mentioned previously.
If you ARE able to remove it, RESTART you Roku to clear its memory cache, via Settings > System > Power > System restart before you attempt to re-install.
I can look all day long for the channel, regardless of where I look, the Topic streaming service is no longer available on Roku. You'll not find it in the channel store or in the Roku Remote app. Apparently, Roku didn't bother to tell people to remove the channel before they stopped offering the service.