There is nothing confirms Obito cant use Rinnegan techniques but there is however manga pages that confirms he can use them.
First, Madara taught these techniques to Obito[
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Second, Obito has been confirmed to be able to use them[
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Third, we have the Konan's statement saying that anyone with Rinnegan can use them.
These are all confirmed feats and same thing applies for Madara. Only reason they're not using them is because of the PLOT nothing more. Rinnegan used would finish the Naruto series and Kishi doesn't want that so he is restricting them from using it.