So this is my first time using anything which utilizes a control file to set dependencies, at least directly to my knowledge; so if I lack some understanding, I apologize.
I started to do an apt search for the packages in the control file. I guess I don't understand what '+default' means; like in librust-proxmox-apt-0.99+default-dev for example. Does that mean the package needs to be version 0.99 or higher? If that's the case, there are some packages like librust-nix-0.29+default-dev, which I'm assuming means package 0.29 is needed but only 0.26.1-3 is available. There's others as well that have the same concern, but if my assumption is incorrect, then disregard that issue.
Also the package librust-proxmox-base64 doesn't seem to exist; there's a librust-base64.
Another is librust-proxmox-schema-4* looks to want version >=4.1 but only 4.0.0 is available.
I'm assuming there's some pipeline that built POM 0.7.0 successfully using this control file.