1st class lounges are only accessible for passholders in some countries, Italy is not one of them.

No I'm sorry, the Freccia Lounge is only for frequent travelers in Business (1st class) and people with a Ticket for Executive Class (1st +).

https://www.trenitalia.com/it/offerte_e_servizi/sale_dell_alta_velocita.html 

You can use lounges in Austria (quite good, in any larger city) and GB. In FR a very, very few-I think only with ALSO a RES for TGV in the next 2-3 hrs. and in theory in NL on INT trips-but these are sourced out to a kind of ´temp.office provider´ in/nearby stations. Expressly NOT IN DE on DB!

Thank you, everyone.

Your answers were very helpful.