Dear Christoph,
I am a beginner so I can only tell you how I started my classical exploration. May be you find it applicable to you. For me I like my music to have a star of the show. So I did not start out with symphony. My plan was to start out with violin, piano and cello. Once I have injected some easy classical into my blood, I would sink deeper into more complex classical. With these three instruments in mind I ask for recommendation from someone who has a lot of experience in attending live symphony. In my case it was Bonzo. I also know that he doesn't like "boring" classical pieces. So he set me up with some ear catching pieces of violin and piano. After that it is all youtube for me. I search for different versions of those pieces by different musicians. The more I search the more I hear interesting interpretations. I choose music from how it drives me. Some pieces I did not even like at first but then I found them with different musicians or conductors they became interesting all the sudden. I listen a lot of youtube. And one thing about youtube is it could lead you to different videos of related music. So one month after, I got so much more music by myself expanding from pieces that Bonzo gave me. I keep listening to what people suggested Beethoven included. But I only follow what drives and makes connection with me. I have not been driven by Beethoven yet. I like Bach, Tchaikovsky, Mendelssohn, Mozart, Rachmaninoff, khachaturian, Dvorak, Schubert and keep adding on. Each composer is played differently by conductors and musicians so there is alot to dig into. Digital is a gateway to new music. I used to stream Tidal but now only do youtube. Youtube shows comments of viewers. Most comments are junk. But some time they mention or recommend different pieces so I track after those too. Fun actually. You are accustom to streaming and have an excellent digital front. So it is even easier for you to get into. Have fun exploring.
Kind regards,
Tang