I've been using Hype for … oh golly, since version 1.0. I've never seen it flat-out incompatible with any OSX. What 'changing a comma to a period' has to do with anything at all is utterly beyond my capacity to grasp.
Dropbox's decision is completely beyond the control of Tumult. Dropbox owns their servers and their bandwidth. How they choose to use their servers and their bandwidth is their decision, not anyone else's.
The discontinuing of HTML rendering by Dropbox was announced six months ago now, so it's not exactly breaking news any more. That you didn't take measures, in September of 2016, to factor in the repercussions of a decision that was utterly beyond Tumult's ability to control is the fault neither of Tumult, nor of Dropbox.
There are myriad relatively inexpensive FTP apps (such as Flow) or, of course, the free built-in FTP program available in the OSX terminal window, that can provide you with fast, reliable file transfer service to any test folder you care to name in any web server you own or have administrative access to. It doesn't take even half a day to set something like that up, let alone half a year.
I understand you're frustrated, but the source of your frustrations is not owned by anyone at Tumult, and is only somewhat nominally owned by Dropbox.