You may have seen this, but certain single board computers have a Raspberry Pi compatible GPIO pinout which certain shields such as Hi-Fi audio DACs designed for the Raspberry Pi can also be used on certain other units; certain units may not implement certain hardware functions (most commonly, GPCLK - General Purpose Clock output which there is little or no documentation for this function as far as I know) on GPIO pins corresponding to the Raspberry Pi and/or these functions may be on different pins and that logic levels for certain boards may differ.
Here is a list of single board computers with absent hardware functions and/or hardware functions on different pins compared to the Raspberry Pi (unless noted, all are fitted with I2C (two buses), GPCLK (General Purpose Clock), SPI (with two hardware selects), PWM (two channels), UART and I2S Audio as per the Raspberry PI GPIO configuration):
Asus Tinker Board: GPCLK
Banana Pi: GPCLK, SPI /CE1, PWM
Maximite 2: GPCLK, SPI selects, PWM, I2S Audio
NanoPi: GPCLK, SPI /CE1, PWM, I2S Audio
nVidia Jetson: GPCLK, PWM1
ODROID: GPCLK, SPI selects, PWM, I2S Audio
Rock Pi: GPCLK, SPI /CE1, PWM
So far, all of the boards I have compared have I2C (both buses), UART (data only - certain boards have hardware flow control pins) and SPI (excluding selects) on the same pins.
Any contributions of single board computers with a Raspberry Pi compatible GPIO pinout with absent hardware functions and/or hardware functions on different pins being noted (along with logic levels other than +3.3V being noted) are welcome here.