Are you talking about the current beta version of classic? or previous patches in retail classic?

I don't think they're doing patch notes for the beta, only known issues: https://us.forums.blizzard.com/en/wow/t ... -19/173883

and the not a bug list: https://us.forums.blizzard.com/en/wow/t ... ist/175887.

Any updates will be on the official classic wow forum but they will be few and far between in terms of actual updates/patches. https://us.forums.blizzard.com/en/wow/c ... -beta-test