[mey]

Firefox seems to be respecting CORS, where Chrome does not, which is interesting. As a result the site doesn't work on Firefox. (at least for me).

   Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://www.reddit.com/search.json?q=(site:v.redd.it%20OR%20site:youtube.com%20OR%20site:vimeo.com%20OR%20site:youtu.be%20OR%20site:twitch.tv%20OR%20site:gfycat.com%20OR%20site:streamable.com%20OR%20site:tiktok.com%20OR%20site:livestream.com%20OR%20site:dailymotion.com%20OR%20site:rumble.com%20OR%20site:liveleak.com%20OR%20site:gifs.com%20OR%20site:giphy.com%20OR%20site:redgifs.com%20OR%20site:bandcamp.com)%20NOT%20url:feature=share%20NOT%20url:vm.tiktok.com%20NOT%20url:music.youtube.com&t=hour&sort=comments&sr_detail=on&limit=12&nsfw=no&include_over_18=no. (Reason: CORS request did not succeed).

Edit: As noted below, if you are running Firefox in Strict privacy protection, it blocks the XHR requests. Whitelisting this site will allow it to work.

[glass_of_water]

I had the same issue; I think the error message is wrong. The reason it's not working is that tracking protection is blocking XHR requests to www.reddit.com. If you disable tracking protection or whitelist www.reddit.com it should work.

[mey]

I do have privacy settings on Strict, and clicking the shield indicated reddit.com was one of the ones blocked.

[bogdanteodoru]

For me it works. Just tested on latest Firefox, Mac.