In my experience on my Windows 10 system, text files with a wide variety of Unicode characters across multiple blocks render faithfully within the "Preview pane" of File Explorer.
For sample text files I've just observed in my installation of DOpus (up-to-date, v12.28), very few such characters outside the "rudimentary" (e.g., Latin-based) blocks render correctly within my Lister's Viewer Pane. In general, short strings comprising characters from what I'll call non-rudimentary blocks render as much longer strings comprising nonsensical substitutions of recognizable (but unrelated and — in this context — meaningless) Unicode characters.
In attempts to rectify this, I first went to Text Viewer Plugin configuration and changed the viewer font from Courier to Code2000; this didn't help.
Next, I clicked on the "Assume UTF-8..." option to enable it. That resulted in a very-different looking failed render — character-for-character substitutions of small "placeholder" boxes for the intended glyphs, plus correct glyphs for a tiny proportion of characters from non-rudimentary blocks.
What if anything can I and/or DOpus developers do to rectify this?
...Thx.