Honestly, my current stance on immutable distros is: why don’t you have a mutable distro and just try to follow the best practices without being forced to?

Install flatpaks, use Distrobox when something is only available as a standard package, but doesn’t actually depend on non-isolated system interaction, etc.

This way, nothing breaks the way it does with immutable distros, but you still have a reasonable level of confidence in your system.