Original dislike:

{
  "actor": "https://lemmy.ml/c/asklemmy",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "object": {
    "id": "https://endlesstalk.org/activities/dislike/e1f82f6a-d49b-4dab-b444-36c382f13c5a",
    "actor": "https://endlesstalk.org/u/freamon",
    "@context": [
      "https://www.w3.org/ns/activitystreams",
      "https://w3id.org/security/v1",
      { ... },
        ...
      }
    ],
    "object": "https://midwest.social/post/7242862",
    "type": "Dislike",
    "audience": "https://lemmy.ml/c/asklemmy"
  },
  "cc": [
    "https://lemmy.ml/c/asklemmy/followers"
  ],
  "type": "Announce",
  "id": "https://lemmy.ml/activities/announce/dislike/6896b8ce-026d-463a-a223-ec1a1d444e5c"
}

Undo of Dislike:

{
  "actor": "https://lemmy.ml/c/asklemmy",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "object": {
    "id": "https://endlesstalk.org/activities/undo/a9377c0b-074c-41de-ba99-51eeca323810",
    "actor": "https://endlesstalk.org/u/freamon",
    "@context": [
      "https://www.w3.org/ns/activitystreams",
      "https://w3id.org/security/v1",
      { ... },
        ...
      }
    ],
    "object": {
      "actor": "https://endlesstalk.org/u/freamon",
      "object": "https://midwest.social/post/7242862",
      "type": "Like",
      "id": "https://endlesstalk.org/activities/like/1f0b6132-547e-4fb5-8313-6f7b7f31be6b",
      "audience": "https://lemmy.ml/c/asklemmy"
    },
    "type": "Undo",
    "audience": "https://lemmy.ml/c/asklemmy"
  },
  "cc": [
    "https://lemmy.ml/c/asklemmy/followers"
  ],
  "type": "Announce",
  "id": "https://lemmy.ml/activities/announce/undo/feedfdca-3392-4f7b-a3ce-2306d8981c5c"
}

The original Dislike activity (https://endlesstalk.org/activities/dislike/e1f82f6a-d49b-4dab-b444-36c382f13c5a) has a record at endlesstalk.org, but the Like object’s activity that’s been undone doesn’t (https://endlesstalk.org/activities/like/1f0b6132-547e-4fb5-8313-6f7b7f31be6b just returns ‘No record found’)

I got the same results when I tried this from lemmy.world (but I thought I’d try again from a 0.19 instance)

I found some references to this at the GitHub, but they were issues that were closed off as being fixed, so I don’t know what the situation is with this now.