Optional Dominus Thrax Undercroft Portals in Duviri

When searching I couldn't find a Steam Guide when looking specifically for the Optional Undercroft portals that spawn in Duviri, these are separate from the Undercroft portals that spawn as part of the "Bounty/Story" you have.

Normal and Steel Path result in different Arcane drop lists. Three Optional Undercroft portals will spawn every time you enter Duviri (On The Duviri Experience gamemode only)

Image was taken from the "Interactive Map" on the Duviri wiki page, so all credit goes to them. Linked here.
https://warframe.fandom.com/wiki/Duviri

Map