OEMs are getting in on the act of bringing Android 11 Beta 1 to some of their devices. To date, only OnePlus has released the initial beta besides Google. However, Poco, Realme and Xiaomi have promised to deliver Android 11 Beta 1, too. There is no sign of other OEMs like LG, Huawei, Nokia and Samsung announcing Android 11 beta programs any time soon, though.
https://www.notebookcheck.net/OnePlus-Poco-Realme-and-Xiaomi-all-announce-Android-11-beta-programs.470169.0.html
So the race begins... Actually there's only 3, since Poco and Xiaomi basically will produce the same rom, MIUI. Realme and Oppo would share something similar though they have officially declared not in the same bed anymore. Oneplus would likely win, if not another near to stockish ROM suddenly appears (Nokia, me see you).
Someone needs to tell Xiaomi why the Android One program was created...