Could the Ottoman Empire join the Entente instead?

Could the Ottoman Empire join the Entente and keep Russia supplied?

Theoretically yes, but only after a major change in Ottoman leadership and strategy, making it less plausible than a competent Dardanelles campaign.

Ottoman entry on the Entente side could theoretically change Russia's supply position. The difficulty is that it requires replacing or redirecting the Ottoman leadership and overcoming the empire's strategic conflict with Russia. That is a deeper alteration than changing how an operation already attempted by the Allies was planned and executed. Its plausibility depends on the number and scale of historical decisions that must be rewritten.