How does one verify an app is running of its published code source?
How can users confidently verify that a FOSS application is running from its published source code? Is there a easy way to check this, or is this based of checksum and hashes?
Although I haven't used it myself yet, Guix actually has a feature that lets you "challenge" the build servers to see if your builds match the pre-built binaries (the command being aptly named guix challenge).
Do you use Guix? I've found it quite interesting and I'd love to try it out one day. The thing is, I need the mainline Linux kernel for some proprietary drivers.
For starters, you're not required to install Guix System in order to use the Guix package manager itself; the manual provides instructions for installing it on top of your existing system here if you want to use it but not fully commit (you can do this with Nix too).
Guix allows for adding new sources to pull packages from using channels. The nonguix channel provides the Linux kernel - blobs and all - as well as other stuff that won't be upstreamed, like Steam and NVIDIA drivers.
I recommend this helpful series by System Crafters, which includes a few guides on installing Guix and Guix System with the full Linux kernel.
Just a note if you plan on installing Guix on top though, since I didn't realize you might be running NixOS: according to this discussion, you'd need to take a different route to get Guix working.