How do you make 90 degrees angles when digitizing polygons in QGIS 3.0 or above without any plugins ?
View > Toolbars > Shape Digitizing Toolbar
Then search for the Create Rectangle icon on the toolbar that you just selected to be checked > Add rectangle from 3 points. Now you can digitize buildings with perfect 90 degrees angles !
You might need to merge the polygons but this is the way.
Sorry for asking the question without reading the MANUAL ... im stupid... just played with the settings and found how to do it ;)