Moist of them can be or will be traded on OTC, at least the bigger names. Alternative you can use IBKR to trade HK market.
Do you own the US ADR? Trustee to the ADR holds the shares. It probably won't relist if there is a hard ban, but the trustee should be able to transact the "real" shares in HK and settle the ADR. You might want to put your hands on a copy of the ADR trust and see what it says about a delisting.
I don't own any BABA now...Have had it before and did well with the company. The only China I now own is a small cap mutual fund (FEM). I am familiar with ADR...Own stocks from Japan, Canada, Israel, Great Britain.