Suggestions for first nixie clock kit?

Just to say, it's not really a beginner's kit, but you're going to have to take the plunge for those tubes, they are a bit special. However, the tubes do merit a good home...

Shipping is usually around 5 to 7 days, and you should be fine as long as you put aside a couple of evenings to put it together.

The microwave detector is really out of this world: You can put it inside the case, so the clock just wakes up magically as soon as someone comes into the same room as it, often before you even are in visible range of it.

Note that there is also a small amount of SMD work to be done. You'll need a steady hand and a stout heart. It's not hard, but many people hear "SMD" and run for the hills. It's not really an option to not do SMD nowadays though. The biggest trick is small gauge solder and a pair of tweezers.

You don't need to code anything. The controller and the WiFi module come ready programmed.

The open source thing is for the tinkerers out there who just HAVE to play around with stuff.

If you want to make any old clock, there are a number of options out there with different tubes. But if you want to use the tubes you have, because it makes a good story, then your choices are pretty limited.

Black boards are great until you have to troubleshoot something that requires visually following a trace. If the design is past the prototyping stage and the board house making them can be trusted to not ship any boards with cut traces or other defects than yeah, I love the look of a black board.

While anything is theoretically possible I don't think the Modular - or any clock designed for numeric Nixies - is ideal for conversion to Panaplex. Consider that Panaplex is a segmented display and numeric Nixies are not. At bare minimum the board would have to be modified to use a different decoder/driver and code modified accordingly. I'm not aware of a high voltage 7 segment decoder/driver (7447 is not fit for high voltages) so probably a whole lot of transistors would have to be added too. And so on...

I don't know of a source for Panaplex anymore. I once had a good reliable US source but they sold out of Panaplex several years ago. I scratch-built a couple Panaplex clocks for myself and sold off the few boards and displays I had leftover to fellow hobbyists. I would have to go digging thru boxes to confirm, but I MAY have a set of boards left but no displays.

Panaplex "brand" has changed hands several times, so rather than searching for Panaplex it can be helpful to try things like "Sperry SP352" or "Beckman SP-352" or "Babcock plasma 352" for example. I've read that Babcock still sells them brand new but never could find out where one might actually buy them. One other tip: one huge application for Panaplex was military and high-end civilian avionics gear, much of which is still in service. Somewhere someone is servicing that gear and probably has a stock or a source of displays.

Here's a bit of shameless self aggrandizement: one of my Panaplex creations...