The Music Fidelity Tri-Vista 21 DAC can be compatible with the Bluesound Node 2i through its digital optical output. However, it's important to note that the Tri-Vista 21 does not support MQA decoding, so you won't be able to take advantage of MQA-encoded music from Tidal.
Whether it's worth getting the Tri-Vista 21 or considering newer DAC offerings like the Denafrips Ares or Gustard depends on your preferences and priorities.
If you highly value MQA support and want to take full advantage of Tidal's MQA-encoded music, it would be more appropriate to explore newer DAC models that support MQA decoding.
On the other hand, if MQA support is not a priority for you and you're more interested in the overall sound quality and performance of the DAC, the Tri-Vista 21 could still be a viable option. It has a good reputation and can provide a high-quality audio experience.
Ultimately, the decision depends on your specific needs, preferences, and budget. It's recommended to audition different DAC models if possible or read reviews to get a better understanding of their sonic characteristics and features before making a decision