Over the years I've acquired a number of nice little frequency counters that use nixie tubes for the display. Rather than removing the tubes and remaking all of the supporting electronics, you can simply use the original counter and 'simply' output a number of pulses representing the time. This simple arduino sketch for a esp32 doit devkit v1 compatible board gets the time over NTP and every second toggles an output pin the correct number of times to display the time.