Hey folks!
The guide to setting up a custom domain on CloudFlare at Obsidian Publish says:
Troubleshooting: If your custom domain setup ends up in a redirect loop, it’s likely that the encryption mode in CloudFlare to Flexible instead of Full.
I’m not sure if I’m just having a bad day, but I can’t parse that sentence. I assume you mean:
If your custom domain setup ends up in a redirect loop, it’s likely that the encryption mode in CloudFlare should be Flexible instead of Full.
…or:
If your custom domain setup ends up in a redirect loop, it’s likely that the encryption mode in CloudFlare has been set to Flexible instead of Full.
All I can tell you is, Full put me in an endless redirect and Full (strict) fixed it. 
Thank you for an awesome app!