How to calculate the Aave TVL using Dune analytics?

That's a hard duty given how dune analytics work by events, but in case it helps:

• Events that bring up HF => Supply/Deposit, repayments & liquidations;
• Events that bring down HF => Withdraw/Borrow;
• Also transfers might affect HF, if atokens are transferred;
• And supply only matters for those assets that are enabled (or can be used) as collateral;

Another way, in case its more simple, would be taking into account balance of atokens acting as collateral, versus debt tokens and do the maths from there.