I don't believe any new / changed B737 MAX software or hardware has been approved or issued.
The only changes as far as I know, is to include documentation in the flight crew reference manuals that the MCAS exists, and how it works.
There are probably very serious discussions going on between Boeing and the main certification authorities (FAA & EASA) about how a system that is critical to flight safety can rely on a single sensor (Angle of Attack indicator) input with no redundancy, no 'voting', not even a 'disagree flag'
Just my $0.02
And whether FAA's decision to not require a new type rating given MCAS was the right one. Will be interesting to see if they double down, or ground all MAX until pilots can be trained for a new type rating. So far they appear to be doubling down.
IIRC the upgrade was minor, pilots do the boring familiarity training, also boring, as it was the same aircraft but modified. But it wasn't, the behaviour was not what a 737-xxx pilot expects. This new crash is that same reason, and if so its on the airline. Ethiopian has an apparently good record.