It seems like AMD’s Ryzen 4000 desktop APUs, like their mobile counterparts won’t include PCIe 4 support, and rather stick to the older PCIe 3.0 standard. Furthermore, the chips will also lack x16 slots for discrete graphics cards and will be limited to x8 ones.

This also means that the total number of PCIe lanes is likely to be a lowly eight instead of 16 which is the norm for most modern consumer processors. The result: You won’t be able to connect many NVMe based SSDs if you’re using a high-end dedicated graphics card.
In my opinion, this isn’t a big deal. Most users who opt for an APU will most likely get a midrange or budget card that shouldn’t have any issues running across eight PCIe 3.0 lanes. Furthermore, most budget motherboards don’t support more than two NVMe SSDs, so it shouldn’t be a major issue there either.
AMD Ryzen 7 4700G Spotted: 8 Cores|16 Threads up to 4.45GHz and 7nm Vega Graphics
Regardless, I’m still curious whether this decision was deliberately taken or just the result of reusing the mobile Renoir dies.