When I click “+” → Add project → Import from BitBucket server, the displayed list of projects/repositories is incomplete. It looks like the returned result is paged, because the list of project strangely ends at letter D and I have a lot of other projects I have access to. Also using the “search box” seems to only filter through that list.
Indeed, there are only 25 projects displayed initially. There was a bug in searching for repos that was fixed in v8.6 (SONAR-14125). The latest version of SonarQube is v8.8.