Now that the SEC followed through with their rule 15c2-11 change blocking quotes from non-reporting companies, the brokerages are all backing away. I don't know if the SEC realized this would happen but it seems like every online brokerage company's response is to just take their ball and go home.
In recent weeks we've seen announcements from Schwab, TDAmeritrade, and others saying they will not allow clients to purchase non-reporting stocks after August 2021. Unfortunately I don't know of a single online brokerage that will let you buy dark stocks after the rule change goes into effect in Sept 2021.
I was a guest on The Investor's Roundtable the other day to discuss this topic. You can hear the audio here and watch video here. Give it a listen to hear my own opinion as well as some others I really respect. I have to say it was a real trip to be on a panel with my hero Dave Waters of OTC Adventures / Alluvial Capital.