The glyph in the evidence looks like U+232F1 𣋱. Also, the previous source reference for U+232F1 was V0-3962, which is the source reference of this IRG Working Set 2021 ideograph. It is now VN-232F1.

The evidence shows U+232F1 𣋱.

The rationale for the change in source is explained in IRGN2429, which was previously discussed at the IRG. I would argue that the right hand side is 興, but here is another source, Takeuchi Yonosuke's "Tự Điển Chữ Nôm".

I will try to find a clearer image, but note that he clearly asserts that this is composed with 興.

Maybe expand UCV #321 and unify with 𣋱 (U+232F1)?

In the 30 plus years of experience with encoding Nôm we have come up with exactly 5 pairs of characters which distinguish 𦥷 and 興. With the exception of V0-3962 and VN-232F1, all are already encoded: e.g U+2C2D9 and U+2444D. I don't see this as a big win, it would just add another difficult to explain unification rule.