Lightroom now offers several different options for exporting files on iOS and iPadOS including Original, JPEG, TIF, and DNG. First, select the files that you want to export (long-tap an image in grid view to select the first image, then tap or swipe to select additional images), and tap Share. Note: if your device doesn’t support the long tap, tap the More icon (•••) in the upper right when in All Photos or in an Album, tap Select, and then tap and/or swipe to select the desired photos and tap Share).
Choose Export as… from the list.
Select the desired File Type (Original, JPEG, TIF, or DNG).
When selecting JPEG, choose the Dimension (Largest Available, Small (20148 px), or Custom) and Image Quality (compression) settings.
When selecting TIF choose the Dimension (Largest Available, Small (20148 px), or Custom), Bit Depth (8 or 16 bits), Transparency, and Compression (None, ZIP, LZW).
When saving JPEG and TIFF files, tap More Options to include a Watermark, Metadata (All, Camera & Camera Raw Info, or Location Info), File Naming (Original, Custom, or Date Filename), Output Sharpening (Screen, Matte or Glossy Paper, with Low, Standard, or High Amount), and Color Space (sRGB, Display P3, AdobeRGB, ProPhotoRGB).
Note: these advanced Export options are already available in Android and ChromeOS.