I just did this myself on a fresh install of of 21.02.0 so using my experience I updated https://openwrt.org/docs/guide-user/network/wifi/dumbap.
I left in steps and notes that were necessary in the old page, but I also added a lot of specific locations and labels from v21. I think it's fairly easy to locate those on older versions.
What are the swconfig and DSA differences? I'm using an R7800 which isn't on DSA yet, I think.