This post was written awhile ago, but still relevant toward installing LimeSDR on Ubuntu. This was done as a Ubuntu image to be used on a Windows PC using a VirtualBox image of Ubuntu preloaded with LimeSDR resources. It’s the method I’ve used for awhile to make the installation straight. Just do a comparison to how I installed LimeSDR and SoapySDR resources to how you did it and you may find the source of the issue - here’s the link:
Running LimeSDR on Win 10 using VirtualBox/Ubuntu - It's possible
Let us know how you did on this and if there’s any further issues getting the Lime running with Ubuntu…
73 de Marty, KN0CK