Not sure whether this is a CAC or MAC regression, but given the migration from AAC to CAC already involves quite some redirections, it seems appropriate to start reporting it here.
See for example the Email This Issue listing:
The Atlassian Community link on the support tab still links to the old AAC tag addon-com.metainf.jira.plugin.emailissue, and while that tag also exists as the CAC tag addon-com.metainf.jira.plugin.emailissue, the redirection is broken and yields a 404.
And to make sure this is not overlooked, the same problem exists for add-ons that do not yet have a tag, which should yield a respectively populated question form so that users can seed a tag (better yet, each tag should be auto generated upfront to ease monitoring of course, but that wasn't available before either).
See for example the Automation with AWS (JIRA) listing:
The Atlassian Community link on the support tab still links to the non existent AAC tag addon-net.utoolity.atlassian.jira.automation-with-aws-jira, and while that tag likewise does not yet exists as the CAC tag addon-net.utoolity.atlassian.jira.automation-with-aws-jira, the redirection does not yield a populated 'Ask question' form and yields a 404 instead.
I hope it goes without saying that this is is a notable impediment for the support experience of users and Marketplace vendors alike and should be addressed quickly accordingly 
Many thanks,
Steffen