James Stanley has designed and built a generally applicable front panel for almost any Z80 system, if you can get to the relevant bus pins. For extra retro points he’s used design notes from a 1978 issue of Kilobaud magazine. There’s also a video, using the front panel with a modern rc2014 system:
… an excellent article in the June 1978 issue of Kilobaud Magazine. It’s the one starting on page 26: “Home-Brew Z-80 System … Part 1: front-panel construction”. Incidentally, the magazine is a fascinating read just for the products that are advertised in it, even if you ignore the actual content!
AIUI, the front panel uses M1 and WAIT to implement single-stepping, BUSRQ and BUSACK to get hold of the bus, then MREQ to inspect and modify memory or IOREQ to interact with I/O devices.
via Alan Cox on mastodon.