You're wrong here, Twitch doesn't ban gambling streamer e.g. Drake because he's gambling on sport betting, not luck based games e.g. slots, roulette, dice etc. The problem is Twitch banning the site e.g. Stake, if Stake separate his casino site and sportsbook site, of course they will can advertise on Twitch.
What do you mean exactly with this? If Stake, as a separate entity, goes live on Twitch that is okay? Stake is a gambling entity, and it's not safe from Twitch's ban since they are a gambling platform.
Youtube is worst than Twitch, so I don't think there's another good platform for Drake except Twitch since the other platforms doesn't popular.
For now there aren't any alternatives. Twitch is the best out of there
as of now and there's no changing that any time soon. Dlive is a good platform but very few viewers at a time, although I think Drake can pull a lot of viewers since a lot of huge Twitch names in the past managed to pull viewers from Twitch to other live streaming platform (Mixer) in the past with enough hype and advertisement of the switch.