In the "what could go wrong category" for information found on the
interwebs, there is a work around for the missing support for the
0x8688 sensor in the new Gigabyte GIGABYTE X570 I AORUS PRO motherboard.
Out of the box, CPU temperatures/voltages are available (k10temp), as
are GPU temperatures/fan and voltages (amdgpu).  Motherboord and CPU
fans however are missing. To the kernel boot parameters in
'/boot/efi/EFI/Slackware/elilo.conf' add 'acpi_enforce_resources=lax'

image=vmlinuz<br>
  label=vmlinuz<br>
  initrd=initrd.gz<br>
  read-only<br>
  append="root=/dev/sda2 vga=normal ro acpi_enforce_resources=lax"

Then load the it87 module in /etc/rc.d/rc.local (or /etc/modeprobe.d/
if preferred):

/sbin/modprobe it87 force_id=0x8628

to force teh closest comptible sensor ID. Now, I have the sensor data.
I'm not sure how accurate the motherboard temperatures and voltages are,
but the fan speeds appear correct. Fan assignments were determined by
unplugging each one to observe the drop to zero rpm.