We’ve used a paid dyndns account “forever” - but were never able to secure a certificate. I only recently learned certificates were now available (cough,cough) - if we were willing to hand over $60/yr (?).
Now I understand it costs money to maintain infrastructure…but a lot of this stuff looks like “nice work if you can get it”. Perpetual annuities are just ill suited for a decentralized internet.
Unfortunately, my client certificate efforts have come to naught for now 
https://bugzilla.mozilla.org/show_bug.cgi?id=1049176
It’s really, really, difficult for mere mortals to sort these things out. In our case - we’re just trying to secure an old closed family email server. And that’s really, really difficult if you can’t tote around IPsec everywhere: http://www.xoware.com/product/
Being able to provide a certificate for a dyndns subdomain would help us a lot.