I'm using en hikari on Flets Cross (10 gigabit) with v6plus.

I set it up like 2 years ago but this was in my bookmarks: https://zenn.dev/ebi68k/articles/6df7cfec64c281

edit: looking this all up again to refresh my memory, it looks like with my static IP the provider switches from using their default MAP-E to using RFC2473 directly instead, the configuration matches "IPIP" in this guide https://qiita.com/kouhei-ioroi/items/cf0c6228c5c1faef415a