Hi! It sounds like the keyword LINEAR PROPAGATION does what you asked for.
From the dico file of Telemac2d (folder v7p0r1/sources/telemac2d)
NOM = 'PROPAGATION LINEARISEE'
NOM1 = 'LINEARIZED PROPAGATION'
TYPE = LOGIQUE
INDEX = 20
MNEMO = 'PROLIN'
TAILLE = 0
DEFAUT = NON
DEFAUT1 = NO
RUBRIQUE = 'EQUATIONS';'PROPAGATION'
RUBRIQUE1 = 'EQUATIONS';'PROPAGATION'
NIVEAU = 3
AIDE = 'Permet de lineariser l''etape de propagation;
par exemple lors de la realisation de cas tests pour lesquels on dispose
d''une solution analytique dans le cas linearise.'
AIDE1 = 'Provided for linearizing the propagation step, e.g. when
performing test-cases for which an analytical solution in the linearized
case is available.'
Is that what you were looking for? Hope this helps