Troubleshooting “Related Field has invalid lookup: icontains”

Have you tried adding the __fieldname on those Lingua references in the ListinoTraduttoreAdmin search_fields, like:

class ListinoTraduttoreAdmin(admin.ModelAdmin):        
    list_display = ("traduttore", "linguaDa", "linguaA", "prezzoParola", "prezzoRiga", "scontoCat", "scontoFuzzy", "scontoRipetizioni")
    search_fields = ['traduttore__nome", "linguaDa__field1", "linguaA_field2"]