For sure, Spotify is convenient but you own nothing and you locked with a subscription. Also, you listen what they propose. What happens if your favorite band become removed from their library?

I still buy few albums and keep my library of audio files. (And I get some album for free using the same methods we used back in the days 😏)

Which tool do you use to re-encode everything to opus ?

I tried with ffmpeg and it works but I had many issues with covers.