Tumblr’s move to WordPress and fediverse integration is ‘on hold’
In the meantime, however, "I think if there was a big push to implement fediverse, we would just do it on the Tumblr code base," according to Mullenweg.
https://www.theverge.com/news/695124/tumblr-wordpress-automattic-fediverse-integration-on-hold-decoder