Teensy 4.1 serial communication with 7N2 (7 databits no parity 2 stopbits)
There is no difference between 7N2 and 8N1. You just have the most significant bit of your data value being the first of the two stop bits.
To transmit just set the most significant bit to 1.
To receive just ignore the most significant bit.
For example:
Serial.write(val | 0x80);

And:
uint8_t val = Serial.read() &amp; 0x7F;