My Oppo is a bit too bright

An external DAC using the AKM AK4490-series DAC chip might provide the sound you’re looking for. The Schiit Modi 3 at $99 is a bargain but bested by the new Modius at $199. 15-day money-back guarantee if not satisfied.

Another option is the use of an equalizer for the digital side. The 4-band Schiit Loki at $149 might be a good low-cost solution. Same guarantee.

If you feel in a spendy mood, the RME ADI-2 DAC ($1149) with AKM DAC chip and Bass,Treble, Loudness and 5-band equalizer controls might be the ultimate solution.

As I discovered, it doesn't take much these days to get a DAC that will outperform the DAC section of the Oppo 105.  So I agree with the others that an external DAC may get you what you are looking for.  But I disagree on the suggestion that the fault lies with the ESS chip.  Some of the best DACs out there use ESS chips.  And extensive modifications of the Oppo DAC section using the same chip have done very well.  The secret is in the implementation.  You have a very good analog set up.  The Oppo is like a Swiss knife.  It does a lot of things pretty well, but can be bettered for particulars.

So I'll be honest, I rarely use the Oppo for CDs anymore. Since I have lostless Tidal, I mainly use it to stream tracks from that service, tho I still play a CD every now and then. If I were to maybe sell my Oppo and invest in just something to stream Tidal (or another streaming service), what might you recommend?

Simao maybe try dark sounding cable like Audioquest for my taste they are full sounding, they are solid core, Belden are strand I think.

the consensus was the the digital end was too bright and brittle.

Compared to analog? Situation normal.