dnsmasq documentation, only using the entire expression
/#/ as a domain is treated to match any domain:
(..) /#/ matches any domain. Thus --address=/#/184.108.40.206 will always return 220.127.116.11 for any query not answered from /etc/hosts or DHCP and not sent to an upstream nameserver by a more specific --server directive. (..)
Accordingly, a quick test adding your line to my configuration resulted in failure:
pi@pi-hole-v5:~ $ nslookup doesn-tmatch.googlevideo.com 192.168.0.13 Server: 192.168.0.13 Address: 192.168.0.13#53 ** server can't find doesn-tmatch.googlevideo.com: NXDOMAIN
As Pi-hole embeds a tailored version of
dnsmasq, you cannot simply switch to another
However, if you are able to determine a sufficiently selective pattern for subdomain names to block, you could add them as a Pi-hole regex filter.