Make sure no other DHCP server is active on your network!
You could also check with below:
pi@ph5:~ $ ip -br -4 a s eth0
eth0 UP 10.0.0.4/24
pi@ph5:~ $ sudo nmap -e eth0 --script broadcast-dhcp-discover
Starting Nmap 7.70 ( https://nmap.org ) at 2020-08-30 21:42 CEST
Pre-scan script results:
| broadcast-dhcp-discover:
| Response 1 of 1:
| IP Offered: 10.0.0.29
| DHCP Message Type: DHCPOFFER
| Server Identifier: 10.0.0.4
| IP Address Lease Time: 2m00s
| Renewal Time Value: 1m00s
| Rebinding Time Value: 1m45s
| Subnet Mask: 255.255.255.0
| Broadcast Address: 10.0.0.255
| Domain Name Server: 10.0.0.4
| Domain Name: dehakkleaar.nl
|_ Router: 10.0.0.1
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 2.89 seconds
You can install nmap on the Pi-hole host with below:
sudo apt install nmap
You might also want to redact the MAC addresses from the tail output you posted above.
We are only interested in the first three octets eg. c8:3d:fc:xx:xx:xx that define the vendor:
pi@ph5:~ $ sqlite3 /etc/pihole/macvendor.db "SELECT mac,vendor FROM macvendor WHERE mac LIKE 'c8:3d:fc'"
C8:3D:FC|AlphaTheta Corporation