Very interesting thread. I learned a couple of new things. Recently I scored a deal on Lumin U1 Mini, and apart from the dumb app (iPhone anyway) and the ethernet-only option, I found it was no real meaningful upgrade from Lindemann Limetree Bridge II. To me, the latter was a huge upgrade from Node 2i, which I won't touch every again. I like German simplicity and manufacturing: so Limetree feeding into the loved-for-a-reason RME ADI2 DAC. This combo is very, very good for the price.
Innous Zen MK3 was my other option, but I think the real sonic difference comes up the chain from an amazing DAC. Among streamers, Limetree Bridge is already great and any incremental upgrades will be marginal. The DAC however can really change what you hear - sound stage, clarity, transparency, etc.