To setup K3S platform for Istio the command is
curl -sfL https://get.k3s.io |INSTALL_K3S_EXEC="--no-deploy traefik" sh -
Then you can deploy Istio pretending you are using a standard Kubernetes installation.
(note you have to install yourself Kubernetes addon like dashboard)
Is it possible to add the K3S to the listed platforms?
there is no problem with installation; but there are problems with kiali configuration (see this thread )