Apparently so. Neither LibreWolf nor AppImage are run by Canonical, so your choice to run unsupported software on an unsupported system is entirely on you.

LibreWolf’s site says this (emphasis mine):

Most AppImages run on recent versions of Arch Linux, CentOS, Debian, Fedora, openSUSE, Red Hat, Ubuntu, and other common desktop distributions.

Even if it is a bug, why should someone else put in more effort to fix it than you’re putting in to maintain your own system?

And you never answered the question.

Honest question, what’s keeping you on such an old version? Standard support ended over a year ago. Sure, there’s “pro” updates, but why bother if you can move to the next LTS?

It has abysmal support. All the places you’d need it to work without anything special, like link recognition in messaging apps and email clients, it rarely does. Even apps that could make good use of specific locations for inputs often don’t register a handler for the scheme. It’s been that way for years, and I don’t expect it to get a whole lot better.