There is no limit - it's ID dependent
If I read everything correctly, when I want to use LR CC mobile on an android tablet I have to deactivate it on my Windows desktop or notebook. So an activation on my phone or tablet counts as one of the two allowed activations. This seems to go counter to the advertising which claims use it anywhere on any device. Since I do all of my real photo editing on my desktop, sounds like it isn't worth the trouble to put LR CC mobile on any of my devices. I have OneDrive with 1TB of storage as well as Google Photos and Amazon Photos for storage so no net gain.