Documentation very briefly mentions DoH but it's not clear whether pihole is a DoH client or a DoH server, plus it seems very hackish. Nothing is mentioned about DoT though.
DoT is used at least on mobile OSes. DoH is favoured by browsers.
Pi-hole provides 'plain DNS', i.e. served from port 53. It can use various upstream sources, but usually requires some sort of 'connector' if you want it to reach them via DoH/DoT.
If you want to serve DoH/DoT/DoQ, you can also use other applications to achieve this. I use CoreDNS to serve up DoT/DoQ and a simple Python DoH proxy behind my lighttpd instance.
There are many options, but they are not part of core Pi-hole.
The current version of Pi-hole (FTL v6.7) has no support for DoT nor DoH, neither as a server nor as a client.
The upcoming version of Pi-hole, being v7 and still in development, does has built-in DoT and DoH support. Merged to development are DoT, DoH and DoH3, both as a server (your phone/browser's communication to Pi-hole) and client (Pi-hole to a public server). DNS-over-QUIC (DoQ) is still being worked on.