Your debug log shows Pi-hole to be fully operational for both IPv4 and IPv6. (click for log details)
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] spindles-mod.tumblr.com is 0.0.0.0 via localhost (127.0.0.1)
[✓] spindles-mod.tumblr.com is 0.0.0.0 via Pi-hole (192.168.1.76)
[✓] doubleclick.com is 172.217.2.206 via a remote, public DNS server (8.8.8.8)
*** [ DIAGNOSING ]: Name resolution (IPv6) using a random blocked domain and a known ad-serving domain
[✓] sixteenth.pbphgwbr.in is :: via localhost (::1)
[✓] sixteenth.pbphgwbr.in is :: via Pi-hole (2600:<redacted>:f3db)
[✓] doubleclick.com is 2607:f8b0:4008:806::200e via a remote, public DNS server (2001:4860:4860::8888)
However, your router is distributing its own IPv4 address as DNS server via DHCP. (click)
*** [ DIAGNOSING ]: Discovering active DHCP servers (takes 10 seconds)
Scanning all your interfaces for DHCP servers
* Received 349 bytes from eth0:192.168.1.254
Offered IP address: 192.168.1.64
DHCP options:
Message type: DHCPOFFER (2)
server-identifier: 192.168.1.254
router: 192.168.1.254
dns-server: 192.168.1.254
domain-name: "attlocal.net"
--- end of options ---
DHCP packets received on interface wlan0: 0
DHCP packets received on interface eth0: 1
DHCP packets received on interface lo: 0
Nevertheless, your debug log also shows some samples of blocked as well as successful DNS resolutions for a client at .249:
*** [ DIAGNOSING ]: Pi-hole log
-rw-r--r-- 1 pihole pihole 11226 Jul 4 05:08 /var/log/pihole.log
-----head of pihole.log------
Jul 4 04:40:58 dnsmasq[1081]: query[A] www.google.com from 192.168.1.249
Jul 4 04:40:58 dnsmasq[1081]: exactly blacklisted www.google.com is 0.0.0.0
Jul 4 04:40:58 dnsmasq[1081]: query[A] epdg.epc.mnc260.mcc310.pub.3gppnetwork.org from 192.168.1.249
Jul 4 04:40:58 dnsmasq[1081]: forwarded epdg.epc.mnc260.mcc310.pub.3gppnetwork.org to 8.8.8.8
Jul 4 04:40:58 dnsmasq[1081]: reply epdg.epc.mnc260.mcc310.pub.3gppnetwork.org is <CNAME>
Jul 4 04:40:58 dnsmasq[1081]: reply epdg.epc.geo.mnc260.mcc310.pub.3gppnetwork.org is 208.54.85.64
This would be in line with you manually pointing your Samsung at Pi-hole's IPv4 address for DNS.
This will work - as far as IPv4 is concerned.
I've also noted that your Pi-hole is using a public IPv6 address (from 2000::/3 range).
For such a GUA address, both its IPv6 prefix as well as its interface identifier parts may change sporadically or even regularly.
As Pi-hole requires a fixed IP address, you should consider to Use IPv6 ULA addresses for Pi-hole instead - provided your router allows configuration of a ULA prefix.
But more importantly, since your network has IPv6 connectivity, your router almost certainly advertises its own IPv6 address as DNS server (or those of your ISP).
Hence, any IPv6 capable client may by-pass Pi-hole via IPv6.
It is likely that this is what you observe.
To avoid IPv6 by-passes, you've got to configure your router to stop advertising its own IPv6 address and advertise Pi-hole's IPv6 address instead.
If your router doesn't offer such a configuration option, consider disabling IPv6 altogether.
If your router doesn't support that either, clients will by-pass Pi-hole via IPv6.