How to make a curved edge straight

If the distortion is simple pincushion or barrel, you can also correct using the distortion slider in the manual lens corrections even if you don't have a lens profile.

If you mean a slanted edge (buildings looking like a trapezium), then Upright is the tool to use. Curved edges would have to be corrected with a lens profile, or in Photoshop with warp tools, or the 'Adaptive Wide Angle' filter.

Look in the help or find a tuttorial for "guided upright". You can straighten curved edges or leaning buildings or distorted rooms. It's possible to make all sorts of corrections with that tool. It's available in both Lightroom and Lightroom Classic.