GitLab pages but for no particular reason... I use Hugo and want HTTPS on a custom domain so that seemed to be an easy way to do it. Only problem is that GitLab does not redirect to the HTTPS version automatically. I might try Netlify some day if it's as easy as GitLab + has custom HTTPS domains for free.
We do indeed offer free HTTPS and custom domain support (as well as the two together) on our free plan. I haven’t used GitLab Pages myself, so I couldn’t compare further off the top of my head.