Incandescent light bulbs (combined with "light-pipes") has been used for calculator displays [0]. If we're going to even less electronic and more mechanical devices, herkons/relay switches and rotating drums (with engravings) exist. Card-punching devices could probably be an inspiration too.

But all in all, I'd imagine we'd have to settle on scraping the old equipment stocks. I bet there are piles of discarded but still useable CRTs lying around somewhere.

[0] http://www.vintagecalculators.com/html/calculator_displays.h...

Yes, this space is high on tradeoffs.

With plenty of source power, pixel grids are flexible. You can construct these from LEDs and paper, https://www.youtube.com/watch?v=QWGoC-9z2Qw. Or chain together 16x2 displays, or use flip-dot displays if you can source them.

If you are low on power, morse-code over a single LED would go a long way - low on equipment cost. Audio output and radio could also be decent low power outputs.

Seven-segment displays are workhorses. Restrict the interaction to hexidecimal characters.

Other obstacles for post-apocalyptic computing are power and storage.

For power - generation itself could be ok from a bicycle. But you need a way to buffer the power.

For storage - FeRAM should be a good option. Will not decay like conventional disks, so long as you repopulate it every few years.

You bring an interesting point for Collapse OS. For Dusk OS it seems to be imagined for a period where old stuff will still be available, so there will be plenty of old computer screens or TVs around.

I wonder how much power a teleprinter consume? Or a modern version of it?