Having looked into the relevant upstream documentation
By default busybox-ntpd runs as a client and does not serve time. You can set the UCI option enable_server in /etc/config/system (in the ntp section) to enable serving time as well.
That done there is still no server instance running since sysntpd is not enabled to run at boot time and thus needs to be set accordingly (LuCI) or invoke manually (does not survive reboot) from cli /etc/init.d/sysntpd restart
netstat -ulpnwe reveals the server instance up and listening on udp:::123.
Invoking from cli ntpd -d -q is not reporting anything if that is any indication that the server actually works.
When invoking it with -q it would act like ntpdate
Having set this conf it is not apparent though which of the settings are actually being parsed by uci | busybox-ntpd. Albeit reckon that pool instead of server may not work and Foris is throwing an error with the iburst argument.
Summary
config timeserver 'ntp'
option enabled '1'
option enable_server '1'
list interface_listen '192.168.112.12'
list interface_ignore 'wildcard'
list restrict 'default kod notrap nomodify nopeer limited'
list restrict 'source notrap nomodify noquery'
list restrict '127.0.0.1'
list restrict '::1'
list server '0.europe.pool.ntp.org'
list server '0.debian.pool.ntp.org'
list server '0.openwrt.pool.ntp.org'
list server '0.asia.pool.ntp.org'
list server '0.north-america.pool.ntp.org'
list server '1.europe.pool.ntp.org'
list server '1.debian.pool.ntp.org'
list server '1.openwrt.pool.ntp.org'
list server '1.asia.pool.ntp.org'
list server '1.north-america.pool.ntp.org'
list server '2.europe.pool.ntp.org'
list server '2.debian.pool.ntp.org'
list server '2.openwrt.pool.ntp.org'
list server '2.asia.pool.ntp.org'
list server '2.north-america.pool.ntp.org'
option driftfile '/var/lib/ntp/ntp.drift'
option statsdir '/tmp/log/ntpstats/'
option statistics_loopstats_peerstats_clockstats '1'
option filegen_loopstats_file_loopstats_type_day_enable '1'
option filegen_peerstats_file_peerstats_type_day_enable '1'
option filegen_clockstats_file_clockstats_type_day_enable '1'
With the package ntp-utils installed the busybox-ntpd server cannot be queried with ntpq -p, suppose that would require the full ntpd package instead of busybox-ntpd
The upstream documentation then continues
It doesnt support advanced features like query, …
Example (install the real ntpd package (=not busybox-ntpd):
That however appears impossible since TOS 3.11 and hence looks like a bug since both, upstream and downstream, featuring/serving the ntpd package in their respective repos.