is there a way to extract from Bitcoin Core some stats about the totale number of wallets?
There's software out there that extracts this information from
chainstate, so it should also work on a pruned node.
like an historical series of how the number of addresses with greater than zero balance evolved over time?
or just a snapshots of all the addresses balance at a given period of time...
This is more work, it requires processing the actual blockchain. There's software out there for this too.
But:
or to export the DB in CSV or something readable...
Blockchair did this already, and you can easily download it! It's slow, so I created a mirror. You may like:
I have snapshots going back a year (second link), or data dumps per day (last link).
If you only want to count funded addresses, I have data since September 2020:
total_number_of_funded_addresses.txt.