Yes, they are. There are .STL files for a 3D printer available on the bottom of the page.

Selling 3D printed cases is a bad business idea if one has no free 3D printers farm. Printing the case for this keyboard takes 8 hours. My local printhouse charges $6 per hour. Plus $5 for the plastic. Plus 30 minutes of working time to clean/assembly the case after printing. = $60 cost only. Profit? How much one ready to pay for this case?
If one has a printer and wants to build a keyboard for himself, the picture is different - a printer is free, time is free (you can work your daily job when the printer is printing), and there are always leftovers of plastic from other projects, if not, +$5. This is the beauty and power of this project = $5 + switches + keycaps. Of course, in a real world good switches are $40 and good keycaps are $100.
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The first one I built at the beginning of 2021. Since then I have collected almost all Drop MT3 keycap sets and built 5x12 and 4x12 ortho keyboards for all of them. Housings (cyberdeck keyboard), switches, diodes and wires are relatively cheap, keycaps are not so much.

Cyberdeck Mechanical Keyboard housing. QMK firmware.

1. Kailh Box Navy switches, Drop MT3 Dasher Keycap Set
2. Kailh Box Jade switches, Drop MT3 Skiidata Keycap Set
3. Kailh Box Black switches, Drop MT3 White-on-Black Keycap Set
4. Kailh Box Jade switches, Drop MT3 Susuwatari Keycap Set
5. Kailh Box White switches, Matcha XDA Keycap Set
6. Kailh Speed Gold switches, Redsuns GMK Red Samurai Keycap Set Keycap Set
7. Gateron KS-9 Green Switches, DROP Preonic Acute Keycap Set
8. Kailh Box White switches, "Plastic" XDA Keycap Set
9. Zilent® V2 Switches, Astrology XDA Keycap Set
10. Kailh Box Jade switches, Drop MT3 dev/tty Keycap Set
11. Kailh Box Brown switches, Drop MiTo XDA Canvas Keycap Set
12. Drop Invyr Holy Panda switches, Drop MT3 Extended 2048 Keycap Set

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