Generally avoid any albums with generic titles like "greatest hits", "best of", or "music for relaxation", etc, and look for albums that on the cover indicate the composer, the performers, and focus on specific works like "Brandenburg Concertos", or "Beethoven: The Late String Quartets, Op. 125-135".

My area of expertise is specifically Early Music (medieval, renaissance, and baroque periods mostly), and I can recommend some of the bigger labels that are great for these sub genres (as they feature a lot of "historically informed" ensembles with period accurate instruments): Naïve, Naxos, Harmonia Mundi, Accent, Teldec, Alpha Classics, and Alia Vox.

There are streaming apps that are designed for classical music, like Apple Classical. I use it a little for music discovery but I mainly use Apple Music because I had already built out a very extensive chronologically ordered folder and playlist structure to navigate all the classical music in my library (plus Apple Classical doesn't have a desktop version which is a shame).

I've got a bunch of Sibelius recordings - you can't go wrong with anything by Leonard Bernstein.

For a bit of an adventure, there's a decently-curated collection of his piano works: Mustonen Plays Sibelius

I can share the .flac if you like. Also, soulseek.

Labels include Deutsche Grammophon, Decca, Naxos, Warner Classics, Sony Masterworks.

Open the search to at least as early as the 1980s.

Apple Music classic if you want to stream. Soulseek if you want to sail some seas.

Qobuz is definitely better for that sort of thing. I just searched for Sibelius on there, and they have a curated playlist of what seems to be pretty high-quality orchestra recordings. On his artist page, there is also a list of "Editor's choice" recordings, which seem to be hand-picked. Even just looking at the most recent releases, most of them seem to be from proper orchestras.