+These are the five possible situations at the time of bullseye (buster + 1):
+
+* `none`: "merged `/usr`" has been reverted
+* `weak`: both directory schemes are allowed, packages only built on classical hosts
+* `middle`: both directory schemes are allowed, packages can be built anywhere
+* `hard`: both directory schemes are allowed, packages only built on "merged `/usr`" hosts
+* `all`: only "merged `/usr`" directory schemes are allowed, packages only built on "merged `/usr`" hosts
+
+It can be summarized by the following table: