I was in a similar predicament, I went with a 13900KF and a MSI Z790 Edge WiFi DDR4 board (moved from AM4) kept my 4 RAM sticks and just went with the lower (CL16 3600) speed with XMP enabled. It's like within 1% or less than a comparable rig running DDR5 at 4800-5000 speeds. I'm not to beat up about it. Stability is greater than the speed. Plus Intel isn't as fussy about the fast RAM as AMD was. That (RAM stability, or lack there of) was what inadvertently got me to the new platform earlier than expected anyways.
Gold_Sample6554
joined 10 months ago
I had an X370 mobo I got used really cheap to upgrade to something relevant to years ago, I ended up snagging a used 3900X when Ryzen 5000 dropped. I ran that until they updated the BIOS and 5000 series was viable on the same board. Went to 5950X. I had no problems until I upgraded to 6900XT GPU, had tons of gremlins that turned out to be due to the RAM stability/IMC not wanting to run CL16 timings (stock or XMP) with that GPU. Ordered 13900K and DDR4 mobo, migrated RAM and rebuilt PC. If I would have figured out the issue with the RAM sooner, I would have just kept the 5950X honestly. It was a beast. At least with the platform upgrade, I got more M.2 drives and a really solid board layout for my use. I don't regret going Intel but the AMD stuff was also awesome.