P. serrulata var. lannesiana is the species name for L-2 rootstock. L-2 is Krymsk 7 (Prunus lannesiana). Your flowering cherry should be compatible with sweet and sour cherries as it is related to Krymsk 7.
Resources:
Taxon: Prunus serrulata var. lannesiana
Sweet Cherry Rootstock Research
KRYMSK 7 (L-2 cv.)
New Fruit Tree Rootstock
The University of Arkansas mentions Prunus serrulata Kwanzane as sometimes being grafted onto Prunus padus (Bird Cherry) but can also be on it’s own roots.