Is it true that Snap has proprietary server?
The actual package management tools for Snaps - snapd and family - are open source. That's what makes the Snap package management system open source and Canonical is not lying about that.
It is true that snapd is hardcoded to use Canonical's servers for obtaining snaps and the metadata associated with them. And the source for the backend servers is not available as far as I know. Various other parts (e.g., the snapcraft.io website, the Snap store app itself, etc.) are open source. I mean, you could serve deb files from an IIS server, but that wouldn't make the apt package management system closed source, would it?
Can you make snapd work with another backend? Technically, you could read the snapd source, figure out the protocol (which shouldn't be difficult - I think the code is fairly readable), implement your own backend, and build a snapd with a patch to swap the backend URLs. However, nobody seems to have done that so far, and Canonical haven't published a reference implementation.
The Snap Store is run and controlled by Canonical and is not open source. The rest of Snap is open source, meaning the daemon and core software. How threatening this is depends on you POV and has been the subject of much discussion. E.G.
- "Snap v Flatpak v AppImage - In Depth Pros & Cons of Universal Packaging" on youtube.com ,
- Linux Mint forums, e.g. this thread
- Noting that Linux Mint (based on Ubuntu) bans installations of snaps by default (with a hint of how to enable their installation).
As a Linux newbie myself, I've just finished researching snap issues after finding the (LM) program manager doesn't list any snap packages. What I found was that adopting a firm line approach may sever dependency on the Snap Store but replaces it with another problem - in my case missing or receiving out of date packages installed using the Linux Mint package manager:
- The (LM) PM installed a 10.x version of node instead of the current 16.3.1 LTS version,
- The
nodepad-plus-plusworking snap package for Notepad++ (natively available under Windows) was simply not listed. A linux version (notepadqq) can be installed - and I did - but is not a substitute for using the original.
This is where pragmatism and life expectancy comes into play: personally I enabled snaps to install notepad-plus-plus, with which I have decades of experience and consider a "must-have", but would search extensively before installing snaps simply because I can. FWIW I'm not sure if installing node from binaries by running the archive manager GUI as root was a good idea but it got the job done.
;TLDR
Yes the Snap store is controlled by Canonical. Whether that is sufficient reason to compel a move away from Ubuntu is a matter of personal opinion and beliefs, and heavily depends on how and why you select and use snap packages in general.