An issue has been identified in Adaptable versions 2.4.2, 2.4.3, 3.0.3 and 3.0.4 which causes a redirection loop when installing for the first time. If this happens then please patch with: https://gitlab.com/jezhops/moodle-theme_adaptable/-/commit/887e3ca438c2df64556c7f770d3468c86d9bd12b until I'm able to make a new release.
I've pinned this post as it is important. If others need vital information pertaining to Moodle.org plugin database themes pinned for a short term, then please contact a forum moderator, such as myself. But I would not want too many pinned posts.