I have just read that Trainline will be offering tickets for a new high speed service in Spain operated by Iryo at cheap prices. It is part owned by Trenitalia but I assume Interrail passes will not be accepted - does anybody know?
https://iryo.eu/en/we-are-iryo-en/
Also SNCF announce a twice daily Alicante - Madrid service under the Ouigo Espana brand.