The absence of JMAP support seems even more strange when considering that the Thunderbird team is planning to sell email hosting with server software (Stalwart) that not only supports JMAP but seems to have a strong focus on it.

The Thunderbird Pro team even made a blog post today with pictures for the Thundermail account dashboard, one of which shows JMAP info: https://blog.thunderbird.net/2025/11/thunderbird-pro-november-2025-update/