"North Vietnamese PaK-40 guns on parade in Hanoi during the late 1950s or early 1960s, these guns were not used at anti-tank role but they were used as coastal gun and Artillery".
https://preview.redd.it/7s710x2wz517...=webp&8c06cbe0
"A 75mm pak 40 of a North Vietnamese militia forces".
https://i.redd.it/xmmb8kp9k3551.jpg
I think on a more practical note in one of his PDFs James Langham has Soviet / Russian / etc forces using this in T2K, with some captured and aquired ones been used by whomever can:
https://en.wikipedia.org/wiki/76_mm_...n_M1942_(ZiS-3):
And that link has it in use from '2015 to the present' here
https://en.wikipedia.org/wiki/Yemeni...2%80%93present)
Strangely one Wikipedia site has the civil war starting one year before other has the weapons' use beginning...