I have tried to establish that in How Solid and ActivityPub complement each other best and on SocialHub with a related topic:
There is community interest, and some projects explore combining the technologies, like @srosset81 with ActivityPods.
From the Solid Project itself there wasn’t much interest it seemed, maybe due to time constraints or different directions. ActivityPub spec co-author Christine Webber (@cwebber) has tried to reach out to discuss ACL’s but AFAIK was never contacted. They are currently working on Object Capabilities (among others) in The Spritely Networked Communities Institute.