  The generic scale-invariant theory of an axion and a dilaton coupled to
gravity in $d$-dimensions is generalized to a `universal' one-axion model with
two dilatons that reproduces itself under consistent
dimensional-reduction/truncation. Flat FLRW cosmologies are shown to correspond
to trajectories of a three-dimensional autonomous dynamical system, which we
analyse with a focus on accelerated cosmic expansion, deriving the precise
swampland bounds that exclude eternal acceleration. We also show that for two
sets of values of its three independent parameters, the model is a consistent
truncation of maximal `massive' supergravity theories arising from
string/M-theory; for these maximal-supergravity parameter values the FLRW
cosmologies include some with a transient de Sitter-like phase, but not the
recurring de Sitter-like phase or eternal cosmic acceleration that is possible
for other parameter values.
