Note that this would also require your upstream DNS resolvers to support DoT. While becoming more and more common, you still want to verify that your chosen DNS resolver does support DoT.
You might want to search the forums for this.
There are a few topics around that deal with DoT and its implications for Pi-hole (e.g. Implement DNS-over-TLS capability in Pi-hole has a vivid discussion why DoT won't become an integral part of Pi-hole soon, and Pi-hole for DNS-over-TLS - the Simplest Way has a short example for using a third party package).
The easiest way to enable DoT in a standard Pi-hole setup would be if your router supports DoT:
Set your router as upstream DNS for Pi-hole, and let your router handle DoT traffic to its upstream DNS servers.