Lightroom uses sRGB profile for Jpeg exports and the exports from Lightroom CC mobile do not use the target color management model like the one on your desktop based Mac does.
OS application development uses the targeted color management model. Your content is matched to the sRGB color space on the authoring platform. This matching is not performed dynamically on the iOS device. Instead, it happens during authoring on your Mac OS X desktop.
Targeted color management may also occur when you sync content to your mobile device. In fact, iTunes running on the desktop provides color management to the iOS targeted color space when you sync content from iPhoto to your iOS device.
What this means is that, when you sync your pictures to an iOS device using iTunes, your Mac is doing all the heavy lifting behind the scenes, making sure the images are color-matched to the sRGB color space before copying them over to your device.
Here's couple of article's I'd recommend you to review:
Hope that helps.
So, if I have in my OSX High Sierra a ProPhoto profile color and I´m working with lightroom CC, I watch the photos in Prophoto and if I export the JPG, It exports a JPG with SRGB profile? Have I understood correctly?
But working with lightroom web app and Ios app, there is no way to export a jpg with SRGB profile?