A proper Unix keyboard layout must have escape next to 1 and control next to A.
Compared to the usual ANSI layout, backquote is displaced from its common position next to 1. But a proper Unix keyboard should cover the entire ASCII repertoire, 94 printing characters on 47 keys, plus space, in the main block of keys.
To make a place for backquote, we can move delete down a row so it is above return, and put backslash and backquote where delete was.
(Aside: the delete key emits the delete character, ASCII 127, and the return key emits the carriage return character, ASCII 13. That is why I don’t call them backspace and enter.)
This produces a layout similar to the main key block of Sun Type 3, Happy Hacking, and True Fox keyboard layouts.
Personally, I prefer compact keyboards so I don’t have to reach too far for the mouse, but I can’t do without arrow keys. So a 65% keyboard size (5 rows, 16 keys wide) is ideal.
If you apply the Unix layout requirements to a typical ANSI 68-key 65% layout, you get a 69-key layout. I call it unix69. (1969 was also the year Unix started.)
I have arranged the bottom row modifiers for Emacs: there are left and right meta keys and a right ctrl key for one-handed navigation. Meta is what the USB HID spec calls the “GUI” key; it sometimes has a diamond icon legend. Like the HHKB, and like Unix workstations made by Apple and Sun, the meta keys are either side of the space bar.
There are left and right fn keys for things that don’t have dedicated keys, e.g. fn+arrows for page up/page down, home, end. The rightmost column has user-programmable macro keys, which I use for window management.
unix69 vs ansi 65%
ANSI 65% keyboards have caps lock where control should be.
They have an ugly oversized backslash and lack a good place for backquote.
The right column is usually wasted on fixed-function keys.
It’s common for 65% keyboards to have 67 or 68 keys, the missing key making a gap between the modifiers and arrow keys on the bottom row. I prefer to have more rather than fewer modifier keys.
unix69 vs true fox
Matteo Spinelli’s Whitefox / Nightfox “True Fox” layout has top 2 rows similar to unix69. It sometimes has backslash and backquote swapped.
Unfortunately it has caps lock where control should be. Its right column is wasted on fixed-function keys (though the keyboards are reprogrammable so it’s mainly a keycap problem).
On the bottom row, True Fox has two modifers and a gap between space and arrows, whereas unix69 has three modifiers and no gap.
unix69 vs hhkb
The Happy hacking keyboard layout is OK for a 60% Unix layout. However it lacks a left fn key, and lacks space for full-size arrow keys, so I prefer a 65% layout.
unix69 vs keybird69
Owing to the difficulty of getting keycaps with exactly the legends I would like, the meta keys on my keybird69 are labelled super and the delete key is labelled backspace. I used F1 to F4 keycaps for the macro keys, tho they are programmed to generate F13 to F16 which are set up as Hammerspoon hot keys.
But otherwise keybird69 is a proper unix69 keyboard.