Hello! I've been using openSUSE Tumbleweed as my daily (as much as I can anyway, some things still only truly work best under Windows unfortunately) but here are some things I did to get openSUSE ready for gaming:

1. Open up YaST. I prefer to use KRunner for most of my tasks, and to bring that up I use Windows key + Space on my setup, yours could be different if you've tinkered any.
2. Go to the Software Repositories and ensure that OpenSUSE Tumbleweed Tools for Gamers repo is checked. Close out when done.
3. Open up Software Management next. In here, search for gamescope. Tick the box to the left of the gamescope row. (I don't have mangoHUD installed on my own, but you can search for it and install it too if you prefer. I don't know what it does, so look it up and research it if you think you might want it!)
4. Next, search for gamemode. Tick the box to the left of it as we did previously.
5. Click the Installation Summary tab near the top, then click Accept near the lower right if you are satisfied with what is being installed. It never hurts to always read about whatever you are installing!
6. Open up Discover with KRunner (or however you please) and search for Steam. On mine, there were two options. One option is the flatpak version which I didn't like because of the way it can't interact with the system files as easily as the one provided by openSUSE themselves. So, I installed that one, but of course you can install either one you prefer! I just wanted my folders to be more legible/easily accessible for myself.
7. Depending on what GPU you have, you might be ready for Steam to download some games and play. If you have an nvidia GPU like me, you will probably need to make sure your drivers for it are installed correctly and updated.
8. I recommend you play around with some of the Steam settings, but the ones I want to focus on for you here are the games that aren't native to Linux. For example, Metaphor: ReFantazio does not support Linux out of the box. So, what I had to do was click the game in question, and then click the cog wheel to the right and usually under the banner picture for the game. Click Properties, and then click Compatibility on the left hand side of this window. Tick the box next to "force the use of a specific Steam Play compatibility tool", and now a dropdown box will show up underneath that. Click this dropdown box and notice the options for the version of Proton you now can use. I think Experimental might work for the most part, but for Metaphor I used 9.0-4 (as of writing, and even then I still see some graphical hiccups quite constantly, but I don't want to move over to a different Proton version because of how I have personally set my system up. It shouldn't be as much of a headache for you.) If whatever version you choose to use doesn't work, select another version and keep going until you find one that does work. If none work, I won't be much help, but you can always look into trying through Lutris, as it will give you more fine grain control I believe?
9. Test. Test. Test.
10. Enjoy the fruits of your labor!

Hopefully that helps out some. Generally when I run into a problem, I'll search like so:
how to get xxxx running on openSUSE Tumbleweed? openSUSE Tumbleweed xxxx issue

and so on and so on.

Good luck on your journey!

P.S. Steam can be kinda wonky on Wayland, which I forgot to mention in the steps, but to fix the flickering issue with my setup, I went into Steam's settings > Interface and turned off "enable GPU accelerated rendering in web views" and the flickering stopped.

*Also, I think Wayland works better for playing newer games. I just know that on my own setup, xorg runs like garbage even on the desktop, while in Wayland, it is as buttery smooth as it can be, even better than Windows! So, look up how to change into that mode. You can log out and do it right from the login screen!