The traceroute (symbolic linked to busybox.suid) in TinyCoreLinux 15.x does not support IPv6 address family.
To traceroute an IPv6 address, install nmap and openssl-1.1.1 as an alternative solution:
tce-load -wi nmap.tcz
tce-load -wi openssl-1.1.1.tcz
tce-load -wi openssl-1.1.1.tcz
After installation, traceroute IPv6 address may be achieved by:
sudo nmap -v -6 -sn -n --traceroute 2001:4860:4860::8888
That's it!