My current setup is a TP-Link wireless extender. From that I have my own little network that connects my computer, wireless devices and a Raspberry Pi 4. The RPi4 runs the Home Assistant OS for my small network of lights and switches. The TP-Link extender does not have enough memory to support OpenWRT which means I am dependent on the proprietary android app to configure it.
I thought I could use the integrations in HA to add OpenWRT and Pi-Hole but it looks like those integrations are for communicating with instances and devices not within the HA operating system.
What I was hoping to accomplish was to run HA, OpenWRT and Pi-Hole on the same RPi4 device and re-use the TP-Link extender elsewhere in the house to serve ad-blocked internet that extends beyond my little network of devices.
Would running multiple services like this be too demanding for the RPi4? And if it is possible, where is a good place to start?
Depends on how much RAM your RasPi 4 has. And if you use HA-addons that use lots of RAM. You could also switch from PiHole to AdGuard. The latter is available as a HA-addon.
Maybe have a look at something like Docker to set up containers for multiple services on the same RasPi. Docker can also set up networking so you can route everything through something like OpenWRT.
So today I learned the difference between an integration and add-on in HA OS. Adguard seems like the most reasonable solution for me.