A student club in Milano made a really great series on blockchain tech.
Link: https://youtube.com/playlist?list=PLWTCD_J8kOHOeW1u3MH0CyTPT...
There’s also this great tutorial making a uniswap clone that goes through the hardest aspects of onchain development.
Link: https://medium.com/coinmonks/programming-defi-uniswap-part-1...