I don't know about the others, but TD Ameritrade did restrict trading (maybe just buying as well) but only if you were buying on margin. RH is getting ire because they restricted buying for everyone.
Interactive Brokers blocked buying GME stock in non margin accounts. What I hear from twitter the same was for RH.
Correct. If you are in Australia, file a complaint and then escalate to AFCA. This violates the Market Integrity rules which applies to IBKR Australia.
On TD Ameritrade, I had no issues buying and selling (in cash) shares of GME today. I did have to call a broker to sell covered NOK calls though as those gave errors when trying to open the position myself in thinkorswim.
Big difference between halting or restricting volume and preventing a long...