I don't think "unknown" is likely to be confused with the name of a real encoding,
No wait, "likely" is correct, not "unlikely". The point I was just making is it will NOT be confused, unlike [scope](https://github.com/geany/geany/issues/3632#issuecomment-1773950714) where "unknown" is a possible valid scope name.
But the OP was about inconsistencies in casing, and "Unknown" is different to "UTF-8" or "EUC-JP", should it be "UNKNOWN"? Uggg, having typed that, its ugly, no "Unknown" will have to do.