Gear Advice

So I have decided to get back to doing landscape photography, but it seems that Canon has decided after 30 years that they will change mounts to the RF system (been clueless about systems for 10 years). So currently I have a Canon 7D and a 77D with no real quality glass (Tamron 18-400). I want to get into the R5 MKii and L glass 15-35, 24-70, & 100-500, but I do not have $12k to drop at once. My dilemma is what to go for first. If I go for glass, that means getting the EF so I can keep shooting then use a converter for the body later. If I go for the body first, I have a crappy lens (plus still need converter) before getting quality glass. Does anyone have experience using the EF L series on an RF mount? Does it work just fine? I know the RF glass is a little more compact and a little lighter, and specifically designed for mirrorless.

So that is my conundrum, where to start. None of my current gear is worth anything to sell to help pay for something.