I've been using Linux - off and mostly on - since a year after Linus released his kernel, and so have tried a bunch of flavours. I agree with aperson: you'll receive lots of recommendations, but only you know what you like.
My daily driver is Ubuntu on an i5-7200U (Lenovo ThinkPad), and before that it was Kubuntu. My main PC is an i7-7900K, so similarly long in the tooth as yours, and both CPUs run the Ubuntu flavours just fine.
My personal preference is currently Kubuntu (faster, lighter, and fewer "this is how it is, and you'll be glad for it" decisions). But there are so many others to try. Find a bunch that support Proton and gaming, grab their "live CD" versions, and see which ones work for you.