Before installing a pihole (hosted on another machine not my raspberry pi) I used to use my raspberry pi as a WiFi extender (aka enabled the hotspot functionality on Ubuntu) and it used to run flawlessly. After installing the pihole and setting it as a DNS server on my router the hotspot magically stopped proving internet connectivity to the connected devices even though the raspberry pi itself had internet and worked without issues.
Expected Behaviour:
Devices connected on the hotspot having internet connectivity and working with no issues
Actual Behaviour:
Devices connected to the hotspot don't have any internet connectivity whatsoever
WiFi hotspot software frequently conflicts with Pi-hole DNS configuration. They may install configuration files in /etc/dnsmasq.d that are not compatible with Pi-hole.