It is known that there are finitely many square-free integers $d$ for which the ring of integers of $\mathbf{Q}(\sqrt{d})$ is Euclidean under the norm function.
Is there an analogous result for quadratic extensions of $K(t)$, $t$ an indeterminate and $K$ a (finite) field?
Also, can we classify the (imaginary) quadratic function fields that are PID in a fashion similar to the number field case?
I'm assuming the answers to these questions are well known, but my internet search has come up empty.