Flatpaks aren't the only option in Silverblue: you can also layer packages using 'rpm-ostree' (requires a reboot though), and you can also use toolbx (or even better, distrobox) to create an easy-to-use container that you can do anything with. With distrobox you can install an app inside of a fedora/ubuntu/arch/other container, and then use a simple terminal command to expose that app to your host system as if it was installed natively.

I'm on Silverblue and I have mostly flatpaks plus a handful of layered packages as my base system. Then I have a couple of distrobox ubuntu containers for software development (lots of libraries and build tools), music production (with Yabridge and Wine). Because the base system is immutable I've never had a problem that prevented my computer from booting, and if I ever do, it's extremely easy to roll back to before the last update. I've had a couple of issues working with containers in the past, but not big ones, and much of that comes down to my own user error.

I definitely recommend Silverblue for anyone who wants a rock solid, practically unbreakable Linux system.