“Mullenweg did not offer an ETA as to how "ASAP" this support would be added.”
Matt Mullenweg promised ActivityPub for Tumblr in a reply to a user complaining that Mastodon is confusing. No timeline, no spec, no comment from Tumblr. Tumblr downloads jumped 77 percent after Musk took Twitter, so the timing is not an accident. A tweet is not a roadmap. Ask again in a year.