Original Sin Ring not converting extra damage from items an archmage buff

Original Sin Ring not converting extra damage from items an archmage buff, please take a look on it

it seems to convert flat on gear but not extra mods? For example; It does not convert the extra elemental damage from Lightning Attunement support gem

Working as designed.

PoE 2 does not use the same formulas as PoE 1. Anything as extra cannot be converted by normal conversion and all conversions are one time instead of linear.

Off the top of my head, there's only way to convert as extra damage and that's with Embitter support. But that still won't work with Original Sin.