Please check out the discourse posted by Monica at the community hub.

Ubuntu and its flavours will be participating in another ‘Ubuntu Testing Week’ from September 23rd to September 29th. On September 23rd, we’ll be releasing the Ubuntu 21.10 Beta after halting all new changes and between then and the final release 3 weeks later, all efforts are focused on ISO testing, bug reporting, and fixing bugs.
The provided link contains many very useful links and guides.

If you have any questions, would like to step up and help us test this release (any flavor), that would be very much appreciated. Feel free to reply & I'll endeavor to respond. The best place to reach fellow testers varies by flavor, but I'd suggest IRC, Telegram but other options exist too (see links in provided discourse post).