Streaming

As a preliminary step, I’ve connected with Tidal through my Oppo 105D player.
Now, how do I get programming to access extensive Classical repertoire?

Not sure I understand the question. Do you use the Oppo as a streamer? Does it have a Tidal app? In that case I assume you have to turn on the TV and use it to display the menu.
I hope others will now step in, because I don't have an Oppo nor do I use Tidal.

Tidal has one of the worst cataloging systems of all the streaming companies.
You literally have to:
1. Type the composer in the search box
2. Add the type of music (symphony/concerto/etc.) after the name.

You then get hits for albums most of the time.
Spotify has a much better organized catalog, and more complete, too.
Spotify also has a nice little 'Discover' tab that offers music related to what you have been listening to. I discovered lots of interesting new composer using that as well as 'Related Artists' when searching an artist.

FWIW, though you can get higher sampling rates on Tidal on some recordings (like MQA), most of their offerings are at the same 44Khz that Spotify outputs.
@willemj .
I believe he is using the OPPO to connect to the Tidal App. on his Ipad and then outputting to his Schiit Dac.
B

Unfortunately, I have no way of connecting Spotify to my system by WiFi as I can do with Tidal.  Oppo has the Tidal app bundled with it, and I’m streaming through the Oppo. What’s worse is I can’t connect any device to my Gungnir DAC because (just a couple of months after I bought it,) the outlet for the optical cable broke. The outlet won’t hold the cable in tightly.  A washer broke off from the outlet. 
So, at this point, if I want to stream, I’m stuck with Tidal.

I haven’t wanted to send the DAC out for repair, because I’m experimenting with different tubes, and besides, I’m enjoying the system far too much.