If you use the network inspector, you get access to the “hidden”, private GraphQL API Pipefy internally uses. You can use that one too! At least if you are aware of the possibility of API changes, no support, etc.

The card activity (with detauls) can be queried like this:

await fetch("https://app-activities.pipefy.com/graphql", {
    "credentials": "include",
    "headers": {
        "Accept": "*/*",
        "content-type": "application/json",
    },
    "referrer": "https://app.pipefy.com/",
    "body": "{\"operationName\":\"CardActivitiesQuery\",\"variables\":{\"orgUuid\":\"redacted\",\"pipeUuid\":\"redacted\",\"cardUuid\":\"redacted\",\"before\":null,\"pageSize\":30},\"query\":\"query CardActivitiesQuery($orgUuid: ID!, $pipeUuid: ID!, $cardUuid: ID!, $before: Cursor, $pageSize: Int) {
  cardActivities(
    orgUuid: $orgUuid
    pipeUuid: $pipeUuid
    cardUuid: $cardUuid
    before: $before
    pageSize: $pageSize
  ) {
    nodes {
      __typename
      ... on CardAssigneeCreate {
        id
        action
        happenedAt
        userName
        assigneeName
        __typename
      }
      ... on CardAssigneeDestroy {
        id
        action
        happenedAt
        userName
        assigneeName
        __typename
      }
      ... on CardLabelAdd {
        id
        action
        happenedAt
        userName
        labelName
        __typename
      }
      ... on CardLabelDestroy {
        id
        action
        happenedAt
        userName
        labelName
        __typename
      }
      ... on CardAttachmentCreate {
        id
        action
        happenedAt
        userName
        fileName
        link
        cardUuid
        __typename
      }
      ... on CardAttachmentDestroy {
        id
        action
        happenedAt
        userName
        fileName
        __typename
      }
      ... on CardCommentCreate {
        id
        action
        happenedAt
        commentContent
        userName
        __typename
      }
      ... on CardCommentDestroy {
        id
        action
        happenedAt
        commentContent
        userName
        __typename
      }
      ... on CardFieldValueUpdate {
        id
        action
        happenedAt
        beforeValue
        afterValue
        fieldType
        fieldName
        userName
        via
        __typename
      }
      ... on CardMove {
        id
        action
        happenedAt
        oldPhaseTitle
        newPhaseTitle
        userName
        __typename
      }
      ... on CardTitleUpdate {
        id
        action
        happenedAt
        beforeValue
        afterValue
        userName
        __typename
      }
      ... on CardDone {
        id
        action
        happenedAt
        phaseTitle
        __typename
      }
      ... on CardOverdue {
        id
        action
        happenedAt
        phaseTitle
        __typename
      }
      ... on CardLate {
        id
        action
        happenedAt
        phaseTitle
        __typename
      }
      ... on CardExpired {
        id
        action
        happenedAt
        phaseTitle
        __typename
      }
      ... on CardChecklistDestroy {
        id
        action
        happenedAt
        userName
        checklistTitle
        __typename
      }
      ... on CardChecklistCreate {
        id
        action
        happenedAt
        userName
        checklistTitle
        __typename
      }
      ... on CardChildCreate {
        id
        action
        happenedAt
        userName
        cardTitle
        phaseTitle
        pipeTitle
        __typename
      }
      ... on CardEmailSend {
        id
        action
        happenedAt
        userName
        emailTitle
        __typename
      }
      ... on CardInboxEmailReceived {
        id
        action
        happenedAt
        cardTitle
        __typename
      }
      ... on CardInboxEmailSent {
        id
        action
        happenedAt
        cardTitle
        userName
        __typename
      }
      ... on CardCreate {
        id
        action
        happenedAt
        via
        userName
        __typename
      }
      ... on CardDestroy {
        id
        action
        happenedAt
        userName
        __typename
      }
      ... on PublicPhaseFormLink {
        id
        action
        happenedAt
        userName
        cardTitle
        phaseTitle
        __typename
      }
      ... on CardInboxEmailsRead {
        id
        action
        happenedAt
        cardUuid
        userName
        __typename
      }
    }
    endCursor
    hasNextPage
    __typename
  }
}
\"}",
    "method": "POST",
    "mode": "cors"
});