If I understand correctly, with some considerations the Hiby R2
can output LDAC? Have you tried this with the 5909?
I ask because I use a FiiO BTA30 to stream LDAC from my mac, so I can work in the kitchen without wires but still get great sound. LDAC is actually really good imo, and if I had an LDAC streaming portable DAP, I'd probably just stick with that. I'm not sure how much better an experience you're getting plugging the 5909's into the R2? If it were me, the gnawing thoughts about eating up the juice would be a distraction from the sound quality, and LDAC would be satisfactory 99% of the time.
But I don't have an R2 and was wondering about your user experience of LDAC on it.
So, I did some tests today with the R2-II.
First, with the R2-II as a DAP (internal SD) configured as a BT transmitter, an the 5909 connected to the R2-II in LDAC mode. Works fine... I did not experience any issue over a few hours. Range is good, easily 10m / 30ft with a couple of (US-type) inside walls. I left it connected to my iPhone (dual pairing) and when I receive a phone call, the track pauses and resume automatically after the call.
Second test was with the R2-II connected to my Laptop as a DAC/Amp and BT transmitter. No difference... works fine.
Third test was with the R2-II connected to WiFi and configured as BT transmitter and AirPlay renderer. Casting from my iPhone to the R2-II & 5909 worked fine... The R2-II displays the album art correctly. But, It is quite a complex setup: iPhone > AirPlay > R2-II > LDAC > 5909, and although it works, I think I would simply cast from my iPhone to the 5909, even if it's AAC only...
I also try casting from laptop through DLNA but today I had issues. I had DLNA working before, but I know it's finicky, so not really surprised here. I did not spent time investigating.
I also tested with a Shanling M0Pro: slightly more expensive DAP than the R2-II, no WiFi, but very cute and quite a bit smaller. It worked equally well. If anything the range may be a tad shorter as compared to the R2, but not by much. Dual pairing also worked fine. Connecting the M0Pro as a DAC to my laptop and as a BT transmitter also worked fine, but the sequence matters: you need to set the BT connection with the 5909 first since, when you plug the M0 as DAC/Amp, you can no longer exit that DAC screen without interrupting the USB connection..
The M0Pro has a "LDAC HD", I'm not sure how the various LDAC levels compare between the R2-II and the M0Pro. Again, I use mostly my 5909 in wired USB mode...