Observed this on the misskey.xyz since a few days (few Misskey versions ago). The message that Local timeline is down means that it has been optionally disabled.

Loads 'Local' timeline as well as it does the others.
Cannot connect to local timeline. Best visible in the 'Deck' view. This issue seems to not affect http://misskey.m544.net instance for example.
OSX 10.14, Firefox 66b7. Observed since about Misskey 10.84 or so?
Just to be sure, misskey has a feature to disable local-timeline. Now misskey.xyz disables it by the admin.
However, I think "Someting happened :(" message at this context is not kind for end-user. Therefore, app should display a message like "Local-timeline is disabled now" when the timeline is disabled.
@Xeltica Yes, you are right. So I'll make this message better.
I understand now, thank you for explaining this. Feel free to close this issue now as resolved, whenever you wish.
Most helpful comment
Just to be sure, misskey has a feature to disable local-timeline. Now misskey.xyz disables it by the admin.
However, I think "Someting happened :(" message at this context is not kind for end-user. Therefore, app should display a message like "Local-timeline is disabled now" when the timeline is disabled.