It seams the 6PWM code for the STM32G can be reused for the Portenta.
Portenta Advanced PWM timers for Motor control is on TIM1 and TIM8
PH13, PH14, PH15 corresponds to TIM8_CH1N, TIM8_CH2N, TIM8_CH3N
and PI5, PI6, PI7 to TIM8_CH1, TIM8_CH2, TIM8_CH3 (in that order) These pins are available on the 80 pin connectors on the botom of the Portenta and should work for 6PWM pin control with dead_time insertion.
Note: GPIO 2 and 3 respectively PD4 and PD5 can be use for CANFD instead of PH13 on TIM8.