@delphi_coder To add to what @TotalSonic has already mentioned
Some phone manufacturers do provide the sources for their modifies kernels (all should, legally, but only some do unfortunately), but the drivers are proprietary binary blobs without available source code. These drivers are written to work with specific versions of the kernel. They could possibly work with a newer kernel if they were recompiled against itm, but alas, that cannot be done, since the there is no available source code for the drivers.
Something being Ubuntu is not defined by the package manager or the Desktop Environment. Ubuntu Core exists, which does not use apt, and the dozens of flavors, each focussing on a different DE, and some even without any, also show that the DE does not define a distro being Ubuntu or not either. Ubuntu Touch uses the Ubuntu repos for its base packages, and Canonical has granted the project permission to use the name Ubuntu in the name for the OS.