"Lightroom" the 'Cloud based' v5.5 does not have an 'Email' function at the moment.
That function is only available in Lightroom-Classic. (In the 'Photography Plan 20Gb')
You can Share a LINK from Lightroom and provide the link in an email to others- (Copy & paste the link)
If you must attach or embed images in an email, you would need to 'Export' a (JPG) file from Lightroom and then add and send the exported file using your email app.
Regards. My System: Lr-Classic 12.3 Photoshop 24.5, ACR 15.3.1, Lightroom 6.3.1, Lr-iOS 8.0.8, Bridge 13.0.3, Windows-11.