Unfortuntately I’m seeing the same issues in the logs on the Discourse side of this, and you’re not showing up as a follower.
As you can see I just successfully followed from two other mastodon servers. I signed up for an account on mastodon.ie (“irishangus”) and I’m also seeing the same issue you’re seeing, i.e.
[Discourse Activity Pub] Failed to process https://mastodon.ie/users/irishangus: Could not resolve actor
Moreover, this actor issue log is strange, normally mastodon actor uris don’t look like this:
[Discourse Activity Pub] Failed to process https://mastodon.ie/aec0cbc8-c3bd-4eb2-a4f4-f491f8331841: Could not create actor
This all suggests to me that the issue is indeed specific to mastodon.ie. I’ll investigate further tomorrow.