Found that the arduinoexpressif32 framework has some psram functions builtin:
if psramFound() == true, then you can call ps_malloc(), ps_calloc(), and ps_realloc()... but apparently no ps_free(), ps_size(), or ps_avail()
So it's possible and quite easy to allocate the psram of the T-Display S3, but annoyingly not find out how much there is, or to be able to free it if you don't need it anymore.