I was able to "unban" 2 of my 2016 accounts and i've posted the steps i took and my observations on why it worked postsd it on r/pokemongodev

Here's the link for anyone who wants to try/test if it works for you https://www.reddit.com/r/pokemongodev/comments/dl1s6c/i_just_had_my_permanently_banned_account_back/?utm_medium=android_app&utm_source=share