LibreWolf is a Firefox fork with features removed which we don't want (Telemetry, Pocket, ...) and a few (privacy) features enabled (which can be deactivated if they're too annoying). I didn't had any issues with Firefox extensions as well.
I'm currently using it on Debian and it runs smoothly. Recent Ubuntu versions are also supported and you can install them via your package manager, see here.
There are billions of possible hardware configurations and billions of use cases for an OS. No OS will ever be able to work on all of these combinations flawlessly, I'm just saying that on average you have the best chances of everything working out of the box if using Ubuntu and even if not, there are the best chances that you find help online for your problem on Ubuntu, but there are of course cases where other distros will be better suited.
While I personally am a big fan of Arch, it's absolutely not for beginners.
For a normal Desktop user nowadays I think Linux is just not worse than Windows. Don't ask what Linux can do what Windows can't, ask what Windows is doing what Linux isn't: Spying on you, installing software you neither want nor need, forces you to use software you don't want, forces you to connect your local account with an online account, forces recent hardware on you and in the future, forces you to move all your data into the cloud. And all that while charging you a few hundred moneys. Linux just doesn't do that (well, depending on the distro of course).
For newcomers and non-techies I'd recommend Ubuntu or Ubuntu based distros. Plain Ubuntu is the distro which in most parts 'just works'. If you're looking for something which looks more like Windows have a look at Linux Mint Cinnamon. Linux Mint Mate (or XFCE) is a great choice if your computer is a bit older. I also mention Kubuntu because KDE is the a very popular desktop but rather demanding (but also feature rich), it may also feel more natural for people switching from Windows.
All of them will run Steam without trouble, but be aware that playing Windows games on Linux can in some cases be troublesome and require manual fixes. Maybe look beforehand which games are supported how well on https://www.protondb.com/ .