The "update" step is a bit of a "draw the rest of the owl" in the case of major version updates like this 8.x -> 9.x release. It also depends how many features you're using in that cluster as to how complicated the owl is to draw.
That said, I just made it out alright in my home lab without too much hullabaloo.
Just with editing the apt sources and running apt commands. There is a nice pre-conversion checker which will alert you to anything special you have to (or may want to) do prior to beginning that process.
That said, I just made it out alright in my home lab without too much hullabaloo.