There are some bug reports about /usr/bin/who failing but they don't seem to be relevant.
https://forum.manjaro.org/t/who-coreutils-9-1-1-is-broken/113675/7
https://bugs.archlinux.org/task/58306
"Changing the GID of utmp to 20 and rebooting restores the functionality of libutempter again."
Before making that change my system has GID 996 for utmp.
$this->bbcode_second_pass_code('', '$ getent group utmp
utmp:x:996:
')
After changing (I edited /etc/group directly)
$this->bbcode_second_pass_code('', '$ getent group utmp
utmp:x:20:
')
File permissions look ok.
$this->bbcode_second_pass_code('', '$ ls -l /run/utmp /usr/lib/utempter/utempter
-rw-rw-r-- 1 root utmp 1536 Sep 5 08:00 /run/utmp
-rwxr-sr-x 1 root utmp 9596 Jun 14 21:14 /usr/lib/utempter/utempter
')
Then I rebooted. But there's no improvement. Still it shows that there may be issues in software outside of coreutils 1.9 and wget 1.21.3.