Language whitelist for the timeline on the landing page

[progval]

Hi,

It would be nice for instances focused on some language(s) to be able to only show this/these language(s) in the timeline that #4122 added to the landing page.
Could a setting be added for admins to whitelist these?

Thanks!

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• I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• This bug happens on a tagged release and not on master (If you're a user, don't worry about this).