Estonia's ASICe containers have solved signing any electronic files/documents. Italy is reinventing the wheel a bit. ASICe as such is actually an official EU standard since 2016 and EU law¹ enforces that such digital signatures have to be accepted in every EU member state. Estonian digital signatures have used another standards before though, first Estonian digital signature was given in 2002.

The ID-card also provides S/MIME should someone want to use it but people usually just use ASICe.

[1] - https://ec.europa.eu/cefdigital/wiki/display/CEFDIGITAL/What...