I believe the still in beta #beta.aveees.DDxx.3 rails/lb are gen 4/5 compatible. I haven't tried them out cause I get free gen3 slides from work and most all aftermarket focuses on gen3.
edit: if you're just getting started, ignore gen4 and print ddxx.2 projects, 17 or 19, just use gen3 parts. It's the current meta for a reason. Very well established, huge aftermarket for the ecosystem. Not to mention the biggest market in the states is CA and gen4/5 is a no-go there. That means most free states prioritize gen3 production.