The principle of "spread across multiple platforms" is fundamentally inconsistent with a "safest holdout".
You need to hedge your bets.
You need to realise that free services can be discontinued, paid contracts can be terminated, content or accounts can be flagged, copyright or patent claims may be asserted (more the former than the latter, generally, but expect patent claims on more capable systems), domains may be hijacked or squatted, and self-hosted systems may be DDoSed, require ongoing maintenance, moderation (if user / third-party content is permitted), etc.
POSSE -- Publish on your own site, syndicate elsewhere -- is probable the most robust option overall.
________________________________
Notes:
1. A Japanese word, often translated as "unask the question". https://www.awakin.org/read/view.php?tid=583
