This task is identical to T388427, but for the communities tab only. As I wrote int that task:
When transcluding a special page that accesses the global state directly, things could break in the most surprising ways due to how special page transclusion works, by replacing the main context of the request. For details, see T290706: Parser code for special page transclusion replaces main context.
This task encompasses investigation and rectification of any issues with the communities tab of Special:AllEvents related to these problems.
One such example is that we cannot use OOUI widgets, because the OOUI theme singleton is global. Instead, we would need to either use Codex, or omit the OOUI components.