> There are still some processes that require a waterfall method for development, though

Not on the 2-4 hour latency scale of a GitHub outage though. I mean, sure, if you have a process that requires the engineering talent to work completely independently on day-plus timescales and/or do all their coordination offline, then you're going to have a ton of trouble staffing[1] that team.

But if your folks can't handle talking with the designers over chat or whatnot to backfill the loss of the issue tracker for an afternoon, then that's on you.

[1] It can obviously be done! But it's isomorphic to "put together a Linux-style development culture", very non-trivial.