Hello Gullik,
[...] managed to get two phones on the network, though not stable.
It's known issue that LimeSDR is not stable as a PHY for OsmoTRX. I wouldn't expect any miracles, trying it on different hardware, until the problem is investigated and the fix is merged.
[...] the message of a single L seems a little cryptic [...] DLMS <0003> LMSDevice.cpp:102 [tid=3021294672] L
AFAIK, this message comes from the LMS driver, and it means that you're sending TX samples too [L]ate. Most likely, your CPU is too slow. However, you can play with the real-time priority.
I've never seen such messages with LimeSDR though.
With best regards, Vadim Yanitskiy.