This is just a FYI for those using IB for data.
I've been using the IB CPAPI ( Client portal API ) which is a restful json api but I suspect their TWS api is similar.
But for intraday minute data, I'm able to go back to 2020 and for hourly and higher, it goes back 10+ years.
I've had a brief look at the distribution of candles, and spot checked on charts. They are mostly uniform so all indication points to there being quite a bit of free data if you're already trading through IB with market data subscription.
This is a sample of what's in my local postgres db after backfilling for a couple of days, the reliability of their api is a bit of a joke...
The bottom barchart shows distribution. I think that picture still had the double counting bug so you'll see twice the number of expected 30m candles per month but distribution is what I was interested in.