So since RenBTC is not a real bridge and WBTC is centralized due to BitGo, the only safe way to do this would be to immediately sell the wBTC for ETH and hold that on the ETH chain? Or some other stablecoin?

I know that using a CEX is the easiest and safest and cheapest however you would think that by now there would of been a solution already to bridge between the 2 largest crypto blockchains out there.