Russia, at this point, would be hedging its bets and helping both sides, but certainly not with new, state-of-the-art equipment right out of the box.
Russia has quite a problem here. They are hated by sunni muslims. Tartus is their only warm water port, that they have exclusive use of, it is essentially Russian territory.
If Al-Assad falls Tartus will come under assault and the Russians will lose everything.
The Russian Marines are there to defend the port and to evacuate Russians, that’s the purpose of sending half-empty amphibious support ships.
The Russians are fully aware of the embargo, any weapon systems are likely for Russian use to defend Tartus.