Something that I considered doing with a similar laptop, was to use it as a low-end portable gaming system. I’d take a lightweight Linux distro, like the 32-bit version of Q4OS if it’s system requirements are lower than your current setup, and get it loaded with a bunch of games with low system requirements and retro emulators. Obviously, it wont be anywhere near as powerful as your main computer (if you have one) but because it’s portable, there could be some value in having a portable gaming pc (unless you have something like the Steam Deck).

I’m not sure what you mean by tactical shooter but flathub has a subcategory for shooters in the games category. While half of them are source ports of Doom, Quake and some other games, there are a few games I’ve looked into that seem interesting. So far I’ve only played Empty Clip and that’s a pretty good top down shooter with rpg elements but games like Red Eclipse and Tremulous look pretty interesting as well.