TL;DR: Solo dev, still in beta. anidub tells you if a show is dubbed, in production, announced, sub-only, or unchecked, and shows how many episodes are out when a source has counted them. If it's wrong, name the show.
I watch dubs, and the annoying part was never finding the show. It was finding out whether the English dub exists yet. One site still has last season's credits. A news post says the dub is coming and then never updates. The streaming page either lists English or just doesn't mention a language. Half the time the answer is a thread from two years ago.
So I made one place that tries to answer that. I'm a solo dev, and it's in beta. It's called anidub.
Search a title and it returns a status: dubbed, in production, announced, none, or unknown. "None" means a source actually checked and found no English dub. "Unknown" means nobody has checked yet. Those two get mixed up a lot, and mixing them up is how a show gets called sub-only when it was never looked at. If a source has counted episodes, the page shows how many are out.
It doesn't trust a single site. Streaming catalogues, Crunchyroll, and AnimeSchedule count as "you can play this in English today." Reviewed community corrections sit under that. Cast credits from Anime News Network, MyAnimeList, and AniList sit under those. An announcement sits at the bottom. A current streaming listing beats a credit page, and a credit page beats "we announced this." Old reports expire instead of staying up forever. Each title shows which sources it used, so a wrong answer is something you can argue with.
If you already browse on AniList, the browser extension puts the same label on posters and list rows.
This is still in beta, so if you find a bug, or five, name the show. A correction on a specific title is more useful than a general complaint, though I'll take either. Simuldubs, older shows that only exist on disc, and movies seem like the easy places for it to be wrong.
If you checked a title and the status is off, say which one. I'm also curious what you actually trust today when you want to know a show is dubbed before you start it.