Same issue. Takes 10+ minutes to load the initial Tax Form. It works well after it finally gets loaded. I have the latest version of TurboTax 2020 (I update it every time an update comes out) and the latest version of Big Sur 11.2.1. For some reason I keep buying TurboTax. It just get worse and worse every year. This will be my last year. I pray I can struggle through this year. What a shame, It used to be a great product.
