I have created a timelapse using my Canon RP using the time lapse feature. But it seems to have created an MP4 file. LRT has imported it from the card to a folder on my drive, but it doesn't appear to be accessible by LRT.

I can't find a setting on my camera to change the format for the timelapse. Should I just be using an intervalometer to take a series of photos in raw rather than using the timelapse function of the camera?

With most cameras the "Timelapse" feature directly outputs a video, which is not what we usually want, when shooting timelapse.
The beauty with timelapse is that we shoot them in Raw as individual images and have then all option for editing that we also can use for still frames in Lightroom Classic.
If your camera doesn't feature an internal intervalometer, just go for an external one - this will be better and more flexible anyway in most cases. After having shot such a sequence of Raw-Images, just follow the workflow shown in my tutorials: https://lrtimelapse.com/tutorial/basic

Thanks for the reply. That did work. I was excited to see that my camera had a built in feature, but alas it was too good to be true.