The R|Z568M nixie tube can be connected to the electronic driver in several ways – there are original bakelite sockets from the 70s or you can design your own socket using available pin sockets. The original sockets can be sometimes found on eBay, search for “z568m socket”, the photo below was taken from Z568M Socket by “lci_electronics” seller. A better way is usually to integrate the pin sockets straight into your PCB.
We use Harwin H3161 pin sockets for this purpose. They are well made, quite a low cost, and provide excellent support for the tube. Withdrawal force for the single pin is 1N, which makes 11N for the whole tube (1.1 Kg) – far enough to hold the tube firmly in position even upside down. I use 1.95mm drill bit size for mounting holes in PCB made with ENIG surface finish (gold plating over nickel layer) and 2.00mm for boards made with HAL/HASL surface finish. Both surface finishes make the final hole smaller, HAL/HASL layer is thicker, so a bigger drill bit is necessary. The pin sockets are simply pressed into the holes and soldered from the bottom side.
R|Z568M Nixie tube footprint
CAD file: Footprint.dxf