I'm into Linux, but also into Factorio and motorcycles.
Lemmy genuinely is a replacement for r/Linux because the activity here is just as high as there.
But there is very few content about Factorio and motorcycles here. They are communities, but they don't really replace the reddit ones, especially r/factorio.
Edit: Almost forgot about incremental games. Basically no content exists on those here.
As a not really techy person but one who has been cruising online for a long long time I feel Lemmy is a lot like old old Reddit. Reddit was full of techies when I joined. It grew over the years into a bigger thing but it started with a bunch of nerds talking about shit I didn't understand.