Microsoft published a a white paper detailing the security enhancements of the last year. If you are a Power BI admin, or just a Power BI user, this is definitely worth a read.
Alberto Ferrari gives a great introduction to case sensitivity in DAX.
Gartner has released its 2021 Magic Quadrant for Business Intelligence. Microsoft keeps pulling away from the pack.
The SQLBI team (Marco Russo, Alberto Ferrari, et al) have created a web tool called DAX.do. You can navigate there to try out sample DAX measures and techniques without needing an existing data model.
Patrick LeBlanc has a great introduction to slowly changing dimensions.