I also sent this already directly to Joey, but later found this bug report. My take is this:
--- /usr/bin/ts 2019-02-20 22:03:31.000000000 +0100
+++ ./ts 2023-03-01 21:06:41.177886024 +0100
@@ -53,6 +53,7 @@
use strict;
use POSIX q{strftime};
no warnings 'utf8';
+use open q{:locale};
$|=1;
This should ensure that the I/O is treated with the encoding indicated
by the locale, be it UTF-8 or something else.
Alrighty then,
Thomas
