Improve Debian instructions
What does this Merge Request do?
Provide instructions for Debian that allow for choice of using asdf
or not.
Closes: #1056 (closed).
Merge Request checklist
-
Tests added for new functionality. If not, please raise Issue to follow-up. -
This change is backward compatible. If not, please include steps to communicate to our users. -
Documentation added/updated, if needed. -
gdk doctor
test added, if needed.