I would dig around for ways to BYPASS or DISABLE the automatic updates. If that is not possible, it would be a deal breaker for me and I would look into alternatives. After you have learned Ubuntu based distributions, you may consider going to the source: Debian. I am 98% sure the Debian developers would abhor any of the Microsoft influence Canonical/Ubuntu has gained... I have not heard of Fedora or any of the other major players forcing AU on their users.IF you would like something you can really grow into...Try an ARCH based distribution. You can benefit from the Arch user repository (AUR) and then you will not be dependent on snap/flat packs. Snaps can be beneficial in that you can run packages independently of your system libraries but I have not had need for them on Arch systems since almost anything you can want is either in the repositories or in the AUR. For beginners, Arco or Manjaro will be to your liking. Arch based OS will not update in the background. OR... Follow the Arch WIKI and learn ARCH. It is a challenge at first but you will come out of it with a great understanding of how your Linux system works. When problems occur, you will know how to fix them. Arch is an amazing FAST OS. It contains only what YOU WANT. Nothing more, nothing less!Cheers!
You still have control and if the automatic updating of SNAP packages bothers you so much, uninstall snapd.