I get the open source support part of your comment, but you are taking out the fact Steam/Valve has done a lot …A LOT…to get games working on Steam. Additionally, for the first time every they have driving Linux marketshare higher than MacOS as a result. So, to dismiss them completely is wrong. They have done a lot for linux…and linux gaming.
Steam On Linux Usage Spikes To Nearly 2% In July, Larger Marketshare Than Apple macOS
You could go with System76, I think they have a high-end “graphics” laptop, which would be suitable for gaming. Open source company so you are guaranteed everything is compatible with Linux.
However, if money is an issue or you find something else you like, for example the Dell XPS laptops ( in the past have been very compatible with linux,) here is a tool to check the model and/or the parts (important) such as wifi, etc., to see if they are compatible for a lot of laptops.
Linux Hardware Database