I am not sure if this is the best way of achieving that purpose but I always thought of the flat prior as being quite useful for pedagogical/explanatory reasons.
If you want to demonstrate how the posterior extrapolates between a (non-flat) prior and the likelihood then the former can be sampled with pm.sample_prior_predictive but to get the latter I think you’d need to change the (non-flat) priors to pm.Flat and then use pm.sample