Look into LR’s split toning panel. There are even LR presets for various tones, including sepia. BUT, I much prefer using split toning and leaving the upper highlights “untoned.” (Highlights’ hue & sat sliders both at zero). This method is camera agnostic, of course. I’m currently using this technique with some of my GFX images.
I then tone from the upper mids to the shadows. One of my favorite combos produces a dark cocoa type tone of varying depth/intensity. And using the balance slider allows you to select how much into the upper tones your toning penetrates.
In these examples you’ll see different recipes and intensities of my take on toning:
Of course, if you really liked and wanted the “chewing tobacco yellow” tone of traditional sepia, you can do that quite easily as well using split toning - without having the highlights also looking jaundiced.
Let me add that if you “only” want Fuji’s sepia emulation, you can get to Adobe’s version of it in “Camera Faithful” profiles in the develop module. As mentioned previously, the in-camera film simulations on all Fuji cameras are quite good, but are jpeg only. Adobe’s take on Fuji’s film sims are actually quite good, however, and are all accessible via the camera profiles in the develop module.
Rand