I personally think that putting chipmixer behind cloudflare wouldn't be good for chipmixer's reputation... However, putting a landing page behind cloudflare might actually work...
How about this:
- Put chipmixer.com behind Cloudflare, with only a landing page.
- The landing page shows a link to Tor browser, .onion URL and a link to a (newly created) clearnet URL without Cloudflare.
- The URL without Cloudflare can be for instance nocloudflare.chipmixer.com. If there's no DDOS, it's available. During DDOS, the landing page is still available to point towards the .onion site.
- This way, Cloudflare only knows you visited the clearnet landing page.