Issue upgrading from V11 to V12 on Debian

I am working on upgrading from V11 to V12 on Debian.

My first attempt failed, and I have figured out that this is because I have
added extensions to the V11 DB, at least one of which was not installed
using the Debian packages.

So, it looks like i need to install these before doing the upgrade, correct?

This brings up a chicken or egg issue however. We are creating the
extensions, like this:

CREATE EXTENSION emailaddr with schema ica

So, to accomplish this, I would need to create the ice schema, and the user
it "belongs" to before I run pg_upgradecluster. This raises 2 questions

1) Is it OK to create these before doing the upgrade?
2) Does this flag that creating these extensions "in" a schema may be a
long term "bad idea"?

Thanks for any advice n this.

--
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
-- Benjamin Franklin