Prepare the image for FineArt print

Considering the forum you are using, I assume you are using the cloud version of Lightroom. Of course, you realize there are no printing functions in that version. Digital images in general do not have a PPI setting. They simply have pixel dimensions, and you need to ascertain that there are sufficient pixels to support the resolution you require. As an example if you were printing an 8 x 10" image, the pixel count to support a print at 300 PPI would require pixel dimensions of 2400 x 3000 pixels. There is no option to choose 16-bit when exporting JPEG images because the JPEG format is by specification an 8 bit file format. In either Lightroom or Lightroom Classic it is possible to choose Adobe RGB as the color space for the exported file.