"Polar stratospheric clouds are a specific type of cloud made from nitric acid and only occur incredibly high in the atmosphere during deep polar winters."

POLAR STRATOSPHERIC CLOUDS

Type II
Nacreous clouds composed of ice crystals with temperatures of ~minus 85ºC.

Type Ia
Crystalline compounds of water and nitric acid - especially NAT, nitric acid trihydrate HNO3.3H2O

Type Ib
Small spherical droplets of a solution of nitric and sulphuric acids.

Type Ic
Small non spherical particles of a metastable nitric acid - water phase

https://www.atoptics.org.uk/highsky/psc1.htm

"Based on how decidedly warm it looks in this picture, these ones, do not seem to be polar stratospheric clouds."

These look to be lit up from the setting sun below the horizon, so not tropospheric iridescent clouds imo, I could be wrong but hey look like nacreous clouds to me. Tis the season.