hello wm18822827507,
you may using WindowsOS to generate dtsi files from the pinmux spreadsheet, copy those dtsi files to your UbuntuOS.
there’s python script, pinmux-dts2cfg.py to convert them as board configuration files. then you should perform full flash to update the board configurations.
for example,
$ python pinmux-dts2cfg.py [--pinmux] <ADDRESS_FILE> <GPIO_ADDRESS_FILE> <POR_VAL_FILE> <MANDATORY_PINMUX_FILE> <PINMUX_DTS_FILE> <GPIO_DTS_FILE> <VERSION> [--help]
you may also check some similar discussion threads, such as Topic 53026, or Topic 59977 for reference.
thanks