Is the letter ‘i’ pronounced in the words “buongiorno/giorno”?

See a translation

no, "i" is needed to have the sound "j"

as you probably know, italian alphabet misses "k" and "j" (not only, also w,x,y but this doesn't matter at the Moment)

so... we have a problem.
we use c and g to have those sounds k and j, but they also can sound like "tch" and "g"

so... how to manage that? in a bit complex way, but here it is:

sound "tch"

cia - like in ciao
ce - felice
ci - amici
cio - ufficio
ciu - acciuga

sound "k"

ca - casa
che - amiche
chi - chiesa
co - poco
cu - cugino

same with "g", so here sound "j"

gia - valigia
ge - gente
gi - agitare
gio - buongiorno
giu - giugno

sound "g"

ga - gara
ghe - alghe
ghi - ghianda
go - gorgo
gu - guanto