SBC hardware for stratum 0

[Jaap Winius]

Hi folks,

Years ago I wrote a page that describes how to use ntp together with
gpsd and a Garmin GPS 18 LVC to create a statum 0 NTP server. I always
had it attached directly to the serial port on my server machine, but
hardware specs change and my new AMD motherboard no longer has one.
Now my only choice is to use an RS-232 PCIe card instead, but sadly
that's not possible as my design maxed out all of the available PCIe
lanes.

To continue using my old Garmin, an ideal solution would be to find a
low-power, single-board computer that also has a UART 16550A (or
better), an RS-232 interface and a male DE-09 serial port connector.

Does anyone here know if anything like this actually exists and works
reasonably well? Perhaps as a hat for a Raspberry Pi? Or, maybe if
there's a better place to ask this question.

Thanks,

Jaap Winius