Out of the top 15 large and medium-size instances, 3 are currently offline. In the case of lo.t it is only down temporarily for maintenance. However, freak.u has been offline for months and doesn’t show any sign of coming back.

The numbers above are from Fediverse Observer. Numbers of active users do not appear to be reliable for non-Mastodon (i.e. akkoma / plemora / misskey) instances.