Ok, this is what I was looking for.
https://turbotax.intuit.com/tax-tips/general/tax-considerations-for-fantasy-sports-fans/L75xYecdS
For online fantasy sports (and presumably online sportsbooks and online casinos), net profits are to be reported as additional income.
Net profits can be calculated as (Withdrawals + Year End Account Balance) - (Deposits – Beginning Year Account Balance) = net profits.
If net profits exceed $600 in a tax year, a 1099-Misc will be generated. If any individual qualifying win triggers a W-2G, those will be generated as needed.
This is also in alignment with what the online casino confirmed for me.
