I have been using bugreport.apple.com but given that one of the major things fixed in the revised Beta 3 (18A326h) is apparently a Feedback Assistant crash, it has me wondering ... also for the case where something's not a bug per se but feedback, "I think it would be better if X worked like this ..."
WDOT?
Individuals using betas are free to use the Feedback Assistant; Devs can use the 'Report Bugs' link, below right. 8.2018
Edit 12.15.19 - For those that haven't yet been made aware, the bug reporter link below now goes straight to the FA, so...
Stay tuned for a 2021 update to see if the FA lives, or if Apple, in their continuing quest to find things to change yet again, retires the FA and restores 'bug reporter'.