This nixie clock controller contains an attiny microcontroller, a real-time clock, a high voltage power supply, and all the relevant circuity to drive six large nixie tubes. And it's all open source on Github.
This controller achieves near universal compatibility with the use of two separate PCBs. One which contains all the circuitry, and another to hold the tubes. The two boards are simply connected together via 2.54mm pin headers.
This controller still has a few major flaws:
1. No support WiFi or GPS synchronization, built-in RTC has quite significant drift.
2. ICSP via an Arduino or other programmer is required to adjust the time.
3. No system in place to reduce cathode poisoning.