gr-smart_meters is a GNU Radio out-of-tree module meant to contain various decoders for smart meter manufacturers. The initial release contains a decoder for GridStream used by Landis+Gyr.
A guide on what is needed to get this running is available on the RECESSIM Wiki. The decoder is built off of gr-FHSS_Utils by Sandia Labs. https://wiki.recessim.com/view/Gr-smart_meters_Setup_Guide