Add notice about pkg server issues [skip ci]

README.md

@@ -51,6 +51,17 @@ operating system](https://julialang.org/downloads/platform/). Trixi works
 with Julia v1.5.
 
 ### For users
+**Notice: As of Nov 22nd, the Julia package servers seem to ship outdated
+packages. Thus it can happen that adding Trixi as described in this "For users"
+section may not work properly on your machine, giving you the old Trixi v0.2
+instead of the current Trixi v0.3. In that case, all the examples listed here
+will not work due to breaking changes introduced in v0.3.**
+
+**The best options right now are to either use the installation procedure given
+below in [For developers](#for-developers), or to try the solutions discussed in
+the related [issue](https://github.com/trixi-framework/Trixi.jl/issues/354). If
+you have further questions or you are still having problems, please let us know.**
+
 Trixi and related postprocessing tools are registered Julia packages. Hence, you
 can install Trixi, the visualization tools
 [Trixi2Vtk](https://github.com/trixi-framework/Trixi2Vtk.jl)