Indeed, be careful with anything that involves secret bits.
This tool uses proper crypto/rand initialisation of the starting key https://github.com/AlexanderYastrebov/onion-vanity-address/b...
Check out my other vanity generators (they all use crypto/rand):
https://github.com/AlexanderYastrebov/wireguard-vanity-key
https://github.com/AlexanderYastrebov/age-vanity-keygen
https://github.com/AlexanderYastrebov/ethereum-vanity-addres...