This contradicts your observation on Windows clients:
For IPv4 I only have one DNS, however, I may have misinterpreted things at point. So, here they go the DNS entries for 2 windows clients (masking IPv6 entries):
Windows IP Configuration
Host Name . . . . . . . . . . . . : THINKPAD-X1Yg3
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : ibm.com
lotus.com
s81c.com
ibmmodules.com
ibmuc.com
Ethernet adapter Ethernet Intel Card:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) Ethernet Connection (4) I219-LM
Physical Address. . . . . . . . . : 48-xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Ethernet adapter Ethernet Lenovo USB-C Dock:
Connection-specific DNS Suffix . : local
Description . . . . . . . . . . . : Lenovo USB Ethernet
Physical Address. . . . . . . . . : 48--xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : 2806:...:120(Preferred)
Lease Obtained. . . . . . . . . . : Sunday, November 21, 2021 5:31:43 PM
Lease Expires . . . . . . . . . . : Sunday, November 21, 2021 6:31:44 PM
IPv6 Address. . . . . . . . . . . : 2806:...:95b8(Preferred)
Temporary IPv6 Address. . . . . . : 2806:...:fad4(Preferred)
IPv6 Address. . . . . . . . . . . : fd1d:...:95b8(Deprecated)
IPv6 Address. . . . . . . . . . . : fd3d:....:95b8(Deprecated)
IPv6 Address. . . . . . . . . . . : fdb1:...:95b8(Deprecated)
Link-local IPv6 Address . . . . . : fe80:...:95b8%4(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.236(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Sunday, November 21, 2021 5:31:49 PM
Lease Expires . . . . . . . . . . : Monday, November 22, 2021 5:31:50 PM
Default Gateway . . . . . . . . . : fe80:...:49a0%4
192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.10
DHCPv6 IAID . . . . . . . . . . . : 289942243
DHCPv6 Client DUID. . . . . . . . : ...
DNS Servers . . . . . . . . . . . : 2806:...:9a95
192.168.1.10
NetBIOS over Tcpip. . . . . . . . : Enabled
Wireless LAN adapter Local Area Connection* 1:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Wi-Fi Direct Virtual Adapter #3
Physical Address. . . . . . . . . : A0--xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Wireless LAN adapter Local Area Connection* 12:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Wi-Fi Direct Virtual Adapter #4
Physical Address. . . . . . . . . : A2--xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Ethernet adapter Bluetooth Network Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Bluetooth Device (Personal Area Network)
Physical Address. . . . . . . . . : A0--xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Wireless LAN adapter Wi-Fi:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : local
Description . . . . . . . . . . . : Intel(R) Dual Band Wireless-AC 8265
Physical Address. . . . . . . . . : A0--xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
I just noted that in this client, looks it is working ok. I have other one which looks like this:
Servidores DNS. . . . . . . . . . . . . . : 2806:...:9a95
192.168.1.10
2806:...:1
2806:...:9a95
So, when a did a ping I got something that make thing it was my ISP DNS (my mistake!, sorry)
ping -a 2806:...:9a95"
Pinging 2806-...-9a95.ipv6.infinitum.net.mx [2806:...:9a95] with 32 bytes of data
So, besides what you may tell me, looks like IPv4 and IPv6 DNS are correct, right?
This takes my to my original problem, with apple devices, when I reboot the pi-hole and my router, I can see something like this in the DNS entry:
DNS SERVERS:
192.168.1.10
fd1d:...:9a95
2806:..:1
Which is correct, and I can ping local devices. However, if I disconnect the device, then this is what I get:
DSN SERVERS
192.168.1.10
2806:...:1
And I can not contact local devices, I get a "failed to resolve IP address" in my ping app.
Hope this clarifies things a bit, and sorry for my misundertanding.
Thanks!