A method of manufacturing a lighting device, the method including: - providing an elongated laminar substrate having opposed front and back surfaces, - providing at least one electrically-powered light radiation source at the front surface of the substrate, - sealingly encapsulating the substrate and the at least one light radiation source with a protective encapsulation (160, 162a, 162b, 20; 162, 20) light-permeable at the at least one light radiation source to facilitate propagation of light radiation from the device, - including thermally-conductive material in the encapsulation at a position facing the back surface of the substrate, wherein the method includes: - providing a channel-shaped mould including a bottom wall, lateral walls extending sidewise of the bottom wall and a pair of ribs protruding from the bottom wall inwardly of the channel shape of the mould, the ribs defining a central mould cavity therebetween and a pair of lateral mould cavities between the protruding ribs and the lateral walls of the mould, - dispensing thermally-conductive material into the central mould cavity to provide a thermally-conductive filling therein, - coupling the laminar substrate with the thermally-conductive filling in the central mould cavity, - dispensing into the mould a sealing mass to sealingly cover the front surface of the substrate and the at least one light radiation source, the sealing mass penetrating into said lateral mould cavities to provide side extensions of the sealing mass sidewise of and spaced to the thermally-conductive material in the central mould cavity, - disengaging from the mould the laminar substrate with the at least one light radiation source thereon coupled with said thermally-conductive material and said sealing mass, and - dispensing into the spacings between the thermally-conductive material and said side extensions of the sealing mass one of: - transparent or light diffusive material, or - thermally-conductive material. - providing an elongated laminar substrate having opposed front and back surfaces, - providing at least one electrically-powered light radiation source at the front surface of the substrate, - sealingly encapsulating the substrate and the at least one light radiation source with a protective encapsulation (160, 162a, 162b, 20; 162, 20) light-permeable at the at least one light radiation source to facilitate propagation of light radiation from the device, - including thermally-conductive material in the encapsulation at a position facing the back surface of the substrate, - providing a channel-shaped mould including a bottom wall, lateral walls extending sidewise of the bottom wall and a pair of ribs protruding from the bottom wall inwardly of the channel shape of the mould, the ribs defining a central mould cavity therebetween and a pair of lateral mould cavities between the protruding ribs and the lateral walls of the mould, - dispensing thermally-conductive material into the central mould cavity to provide a thermally-conductive filling therein, - coupling the laminar substrate with the thermally-conductive filling in the central mould cavity, - dispensing into the mould a sealing mass to sealingly cover the front surface of the substrate and the at least one light radiation source, the sealing mass penetrating into said lateral mould cavities to provide side extensions of the sealing mass sidewise of and spaced to the thermally-conductive material in the central mould cavity, - disengaging from the mould the laminar substrate with the at least one light radiation source thereon coupled with said thermally-conductive material and said sealing mass, and - dispensing into the spacings between the thermally-conductive material and said side extensions of the sealing mass one of: - transparent or light diffusive material, or - thermally-conductive material. - transparent or light diffusive material, or - thermally-conductive material.