For some reason non-ASCII characters get mangled on macOS in tlclient.log. Example from Swedish locale:
> 2022-07-07T15:58:29: vncviewer[E]: Copyright (C) 1999-2022 TigerVNC-teamet och manga andra
> 2022-07-07T15:58:29: vncviewer[E]: Se bifogad EULA.txt f"or licensinformation.
> 2022-07-07T15:58:29: vncviewer[E]: Se http://www.cendio.com f"or information om ThinLinc.
For some reason, “ö” gets turned in to “"o”, and “å” in to just “a”. Even stranger, “ä” is left alone:
> 2022-07-07T15:58:29: vncviewer[E]: CConn: Ansluten till värd 127.0.0.1 port 49170
Running vncviewer by hand works fine. The data is not garbled as it is printed to the console.
It also doesn't look like this is a NFC/NFD issue. The log file is in NFC (at least the “ä” is). As is the output from vncviewer. And the “ö” isn't really decomposed as that's the regular quote character and not a combining character. It is also before the “o”, and combining characters are after.
No idea what is going on here.