Please Check The Release DEB Package
If I try to download the 64-bit Trenchbroom 2.0 release DEB package, I get a truncated file. It's about 1.5 megabytes, while the 64-bit Beta DEB package is 73 megs. I tried three times with the same result.
There's another problem. The Beta version cannot be installed straight out of the package on systems that don't use libpng12 with that specific version number, which is one of its requirements. My Ubuntu 16.10 installation has libpng16-16 for example.
I don't have a suggestion about the second problem, but you should see if the first problem is on the server end. This is the specific page which gave me the 1.5M file with the Stable Latest link: