My kid has an Amazon kids Fire tablet. It allows parents to prevent specific apps from appearing on the home screen, and it seems to work fine, but it doesn't allow any kind of keyword blocking. For example, I have blocked a bunch of apps/videos/books by the YouTuber 'Blippi', but he releases new stuff all the time, and the new ones often pop up on the home screen. If I could preemptively block everything containing 'blippi' (or any other keywords) my life would be easier.

Regarding YouTube, the YouTube Kids app lets me block videos and whole channels, and it's great. But there is no equivalent functionality in the main YouTube app. On various devices (e.g., Roku, Google Nest) the kid sometimes manages to find some YouTube channels I'd rather they didn't watch. But I have to manually intervene each time, I can't just block those channels from being watched or recommended in the future. YouTube/Google obviously know that it's valuable to block videos/channels, since that feature exists in the kids app, yet they omit the feature from the main app, even for a paying customer like me. It is obnoxious.