Greetings guys.

I want to know some "instrumental" doom metal bands, and of course, the most famous ones
Are you looking for bands that are entirely instrumental, instrumental tracks, etc? If you look into funeral doom and drone doom, a lot of bands have very long instrumental sections within songs and long instrumental tracks. There are some that are instrumental, but most have so little as far as vocals that they might as well be. For example, Skepticism's first album, Stormcrowfleet, which clocks in at just under an hour with a word count of just over 400, which is an average of 7 words for each minute.
There's no such thing; there never was. Where I am going you cannot follow me now.
Satan Worshipping Doom by Bongripper would be my first choice. Earth 2 by Earth, Absolutego and Dronevil by Boris and Flight of the Behemoth by Sunn O)). I could give you several suggestions that have very minimal vocals, like Earth's Pentastar. Black One by Sunn O)) has almost no vocals on side 2. Alot of these groups tend towards more drone than doom on their instrumental albums.
All Drone Doom songs are similar, As they're so minimal. I don't want "minimal" music in this case. I want classic-styled doom (like Black Sabbath, Candlemass, etc.) but instrumental.
I know you said you wanted the 'most famous" instrumental doom bands, but my buddies band, Ultramafic is an instrumental/Black Sabbath-esque band. They've played about 13 shows so far. Check them out and let me know what you think. I linked their bandcamp, which has two of their demos that they recorded recently. I recommend listening to "Farallon".