At my company (BigCo but not FAANG or SV), we have 20% time, but it's more for personal learning than side projects (and when it is projects, it's fine if those are just to learn, and not to help the company directly.)
Execs call it out and focus on it too, so managers will even be happy to hear you're using it (and say "what can we do to get people to feel like they can use it?")
Execs call it out and focus on it too, so managers will even be happy to hear you're using it (and say "what can we do to get people to feel like they can use it?")