I subscribe to the Met Opera on Demand as well as Medici.tv - of course the Met has many filmed opera performances, many in HD video, historical as well as recent, and is a huge resource of operas. Medici.tv has over 80 operas from other companies, mostly European, including three of my current favorites which are Robert Wilson productions. So far, I've watched, Pelleas et Melisande, Madame Butterfly, and Monteverdi's L'Orfeo. Generally the singers and orchestras sound good - but the real treat are the stripped down but fascinating stagings. I find them very effective, but they require singers who can act as well as pull off the stylized movement, not to mention singing the roles.
Some people find them too stark and contrived but I love them. I plan on purchasing Aida, since it is not available from any streaming service I've found, and as many of the others that I can find.