Taylor Swift Madrid Stubhub?

Hi! I am wanting to get Madrid tickets for TS Eras Tour. I see lots of tickets available on Stubhub and Vividseats. I am wondering if these are legitimate or if there are other Spain /european sites that we are supposed to be using for resales? I am also confused about how ticket transfers work if Ticketmaster was the original seller? Thank you for any help/ advice!

edit: I wanted to add an additional point of concern. I read on the Ticketmaster Spain site that they are not currently accepting transfers and that tickets will be voided if they are sold through third party websites (i.e. not Ticketmaster's 'fan to fan' sale)? Does anyone know if this includes stubhub/viagogo ?