There's not a ton of information available on the breakdown of sales by platform, but the data that is out there shows Linux sales usually compromise ~2-4% for cross-platform games [1]. If you get linux support "for free" by utilizing an engine, then absolutely go for it, but even major companies with massively popular games are still skipping out on first-class Linux support [2], due to the low market share.
It's also exponentially harder to make a Linux port for a AAA game than for an Indie game, for many reasons. The most obvious ones being that most indie games are made with an off the shelf cross platform engine (Unity, unreal), and that AAA titles require a lot more hardware resources, and optimization of this usage is often platform specific (what helps OpenGL might not help DirectX, etc).
[1] https://www.gamingonlinux.com/articles/linux-game-sales-stat...
[2] https://www.gamingonlinux.com/articles/president-of-blizzard...