Zorin, Mint and Pop all are Ubuntu based distros that replace snaps with flatpak by default. I don’t know what would make any of those any more difficult than straight up Ubuntu. I’d even argue that most mainstream distros aren’t any harder to use than one another. Most of the differences between traditional distributions are behind the scenes: package manager, init system, default applications/configurations…
Even Arch, which has a reputation of being “hard”, isn’t particularly hard to use. It’s the lack of an installer that makes people freak out. The rest is just Linux. Once you plop in a GUI for package management and a proper desktop environment, from an end user perspective, nothing of it is inherently harder.