Do symbols for legacy computing work with it? Especially the 1/8ths vertical/horizontal blocks?

If you mean the Unicode glyphs listed at https://en.m.wikipedia.org/wiki/Block_Elements they are supported - you just need a display driver that can render them. For example, `twin --hw=xft` (it's the default) or `twin --hw=X11`, both with a font that contains them

Xe means the Unicode block that is actually named "Symbols For Legacy Computing". It's not in the BMP. Some bloke named Bruce was doing TUI windows with scrollbars and sizer/menu boxes some years before TurboVision and code page 437. (-:

Given that it's drawing TUI windows, the MouseText characters for doing that very thing on the Apple IIe would seem even more pertinent.

* https://tty0.social/@JdeBP/114409020672330885