I mean this seriously - you should look into a larger phone like the Pro Max.

thermal envelope is bigger. The mini has the tightest internals so its gonna heat up faster since its the same CPU.

theres really no good answer for your problem but its an intriguing one :-)

Cooling down a component cpu like an intel or Ryzen involves thermal paste between the die heat spreader and heat sink/fan (or de-lidding, in extreme cases) - not something easily accomplished with a mobile phone.

as dumb as this sounds, maybe just point a regular desk fan at yourself/phone while gaming. The airflow will help a bit (but not as effective as your water boarding technique … LOL, i kid, i kid.)