FBA No longer works with Modern Browser

SharePoint 2016 upgraded to the April 2021 CU and now when I open the FBA login page and select Forms base Auth I enter my creds and the page reloads asking if I want to use Windows or FBA. If I open in IE11 or in compatibility mode works just fine

Yes, due to some security changes Chrome made for cookies SSL is now required for SharePoint to login with FBA. If you access the site via SSL, it should continue to work fine.