This is a general limitation that can just go into the main docs. We don't really want links to the support matrix randomly sprinkled throughout the doc.

This is something that is not going to change, unless Submariner suddenly starts supporting everything. You may be told to patch known issues with these types of things, but if it is a general statement, it belongs in the main documentation as a general support statement:

not-all-infrastructure
=== Not all of the infrastructure providers that {acm-short} can manage are supported
Submariner is not supported with all of the infrastructure providers that {acm-short} can manage. Refer to the link:https://access.redhat.com/articles/7073065[\{acm-short} support matrix] for a list of supported providers.

You may not have added this, but can you please move it to the general Sub. documentation, which I think already has a link to the matrix.