import re
my_dict = {'Coronavirus': 'Coronavirus', 'Food3D': 'Food3D', 'insetti':'insetti', 'carnesintetica':'carne sintetica'}
text = '#Coronavirus: ripartiamo dalla Terra.Cosa mangeremo domani? #Food3D, #insetti e #carnesintetica? #NotInDict'
print( re.sub(r'#(\w+)', lambda x: f'< {my_dict[x.group(1)]} >' if x.group(1) in my_dict else x.group(), text) )
# => < Coronavirus >: ripartiamo dalla Terra.Cosa mangeremo domani? < Food3D >, < insetti > e < carne sintetica >? #NotInDict
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