Probably not. The LSB modules refer to "Linux Standard Base", which is a
standard aimed to introduce some level of compatibility between major
distros. A quick search for "LSB modules" suggests that installing the
package "lsb-core" would give you the modules, but that won't give you the
Ubuntu version.
In any case, short of an error, there shouldn't be any way to determine the
Ubuntu base of Trisquel from within. Canonical's (current) license terms, as
I understand it, ban any unofficial respin of Ubuntu from using Canonical
trademarks- which would, presumably, not permit inclusion of information
about the base version of Ubunu used.
However, there's a fairly simple way to determine the base. It's always the
most recent Long-Term Support release of Ubuntu, which is the one with
version <Even Number>.04: for example, Belenos was based on 14.04, Flidas is
drawn from 16.04, and whatever Trisquel 9 is will derive from 18.04, unless
the long release wait for Flidas pushes it back (in which case you'll know
anyway).
