Document that only Comsol 6.0 and newer are "expected to work".

Comsol 5.5 and 5.6 no longer work out of the box as the latest JPype
version (1.6) doesn't support Java 8, which these Comsol versions ship
with.

Author: john-hen

docs/installation.md

@@ -22,7 +22,7 @@ Python, as is the default, to match Comsol's platform architecture.
 
 ## Comsol
 
-Comsol, obviously, you need to license and install yourself. [Versions] 5.6 and
+Comsol, obviously, you need to license and install yourself. [Versions] 6.0 and
 newer are expected to work. Up to version 6.3, they have been successfully
 tested. A separate Java run-time environment is *not* required as Comsol ships
 with one already built in.
@@ -46,7 +46,12 @@ point to the corresponding Comsol folder and give the link a name that starts
 with `comsol`.
 
 ```{note}
-For most users who already have Comsol installed, MPh will work out of the box.
+For most users who already have a recent Comsol version installed, MPh will
+work out of the box.
+
+Comsol 5.5 and 5.6 may work if you downgrade JPype: `pip install "jpype1<1.6"`.
+Newer JPype versions no longer support Java 8, which these older Comsol
+versions ship with.
 ```