snap does not cryptographically verify all packages, unlike apt

This isn't correct. Run snap download htop from your terminal and you'll receive two files: The actual squashfs image that gets mounted in /snap/htop/<revision number> and a .assert file that cryptographic signature data about this snap file. Modify the squashfs image and snap won't let you install it without passing --dangerous to bypass that check, just like apt-get's --allow-unauthenticated.

The problem here exists at a different level: the level of what's getting signed. Conceptually speaking, running sudo snap install htop is a bit like running sudo add-apt-repository ppa:maxiberta/htop && sudo apt install htop. The package is built by the owner of the snap/ppa, and what Canonical is cryptographically verifying to you is that they got this from the owner of the (snap|ppa). This is roughly equivalent to domain verification for HTTPS (the type of HTTPS certificates Let's Encrypt uses).

There are some different security considerations. For a snap, you need to be aware of the publisher each time you install something new. For PPAs, on the other hand, you only have to worry about this when you add a new PPA. However, the trade-off also works in the other direction. One snap can't just replace another snap on your system, whereas a malicious PPA could provide, for example, a malicious libc6 update.

These are both different (and lesser) assertions than what Ubuntu makes with its standard apt repositories. But they are still cryptographically backed.

Those are snaps. I don't use those on my server. AFAIK, they're mostly used for GUI applications. I don't even have a GUI on my server. I wouldn't even know how to install or run a snap from command line.

Most things that run in my server are containerized services that I wrote personally. So as long as there isn't a vulnerability in podman or my reverse proxy, and as long as keep my base containers up to date (they pull the latest base image each time the image is built), I'm mostly fine.