I do also feel like it is more jittery (android 13, jerboa 0.0.35)

As you are running cloudflared in docker container, by default 127.0.0.1/localhost equal that docker container. Easy fix is to add

extra_hosts:
      - "host.docker.internal:host-gateway"

to your cloudflared service in docker-compose. Then you can point tunnel to host.docker.internal and it should point to your docker host instead of localhost of container. (ofc after reloading services by docker-compose up -d)

Another easy solution would be to make your owncast server listen on lan IP of your server, and point cloudflared tunnel to that