Recently switched from GH5 to Canon R5. I just received the new RF 14-35mm f/4L lens and noticed the RAW images show extreme barrel distortion and vignette. I did some research online and apparently this is normal. read a suggestion to enable "Distortion Correction" within camera, but this option is grayed out and cannot be enabled. I checked my firmware and it's at 1.3.1, which I believe is the newest one. Another suggestion was to correct it using "Lens Correction" in Lightroom, but the lens is not showing up on the list of supported lens. I assume this is due to the lens being really new. I would really love to get the camera to process this correction within. Never ran into this problem with my GH5. Is there a solution?
Since it's a brand new lens, I think you'll have to wait for firmware/software updates.
In Lightroom (or Photoshop), you can do some manual adjustments to counteract the vignetting.
Perhaps photograph a grid (filling the frame). Then in Photoshop, apply appropriate distortion filters and note the amount that produces the best result. Then use that as a guide when correcting images. Definitely a manual and trial-and-error process. But something you could try while waiting on said firmware/software updates.
Canon DPP shows the lens in its DLO list, so perhaps you could connect the camera to your computer and use the Lens Registration Tool to upload the correction data to the camera (recognizing that the correction in camera only applies to JPEGs).
Alternatively, depending on how important the canon correction is, you could convert the RAW files to TIFF in DPP and follow up with additional editing in LrC.
"Is there a solution?"
I will bet Adobe and Canon will have lens correction very soon for this lens. Making a zoom lens in the 14mm to 35mm range without distortion is very difficult. While you wait for that, do your own in PS. It isn't that hard and you can do what you think is best.
Choose Edit > Perspective Warp. You can easily adjust the perspective of your images.