Yes a dual citizen can open account at crypto exchanges using the non-prohibited ID.
At time of writing, crypto exchanges that are not operating as a financial institution (bank, broker dealer, organization legally defined as a financial institution) do not have to deal with FATCA requirements. And US citizens that only have balances of crypto assets on foreign exchanges do not need to file FBAR reports.
The AICPA Virtual Currency Task Force reached out to Treasury’s Financial Crimes Enforcement Network (FinCEN) to help practitioners answer this question. FinCEN responded that regulations (31 C.F.R. §1010.350(c)) do not define virtual currency held in an offshore account as a type of reportable account.
Foreign crypto exchanges are banning US citizens to comply with/avoid a very different set of regulations.
These typically come down to the US regulatory ambiguity around margin requirements, along with the US regulatory ambiguity of the assets they are trading.
Merely making a good faith effort to block Americans absolves them of liability. There is no legal consequence on the citizen for having access, and no legal consequence for the citizen for circumventing a block.
As such, doing whatever you need to do to have a working account on those exchanges is good enough. If you are actually a dual citizen, the answer is yes, you can have an account.
Don't tell them you are an American and don't consistently access from a US IP address.