Has the Covid unemployment tax break (officially called Unemployment Compensation Exclusion, up to $10,200, I believe) been implemented in TurboTax yet?

Not yet.  Once the changes have ben programmed and tested, the IRS (and states as applicable) must approve them.

Just checked today, March 22, and the unemployment compensation exclusion is now incorporated, in the online version at least. If your AGI is under $150,000, up to $10,200 of 2020 unemployment insurance income is now free of federal tax. You have to declare it as income but it gets offset with a credit/adjustment which will appear on Schedule 1.