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 . <EOS>