Yes, this is true.
I never used cloudflare before, then i must transfer all domains to cloudflare to get this working for every domain hosted by imscp.
As i see on cloudflare free its not possible to take his own SSL Cert, so that it could not come into question for me. personally.
Is bit difficult now in this case to solve the problem with https and ServerDefaultPage
BTW: i hope you guys understand my non-google-translated english lol