A bit off-topic, but I would like to reply on this particular point: the “semtech stack” is not more or less dead, the last release came out 22 days ago. Or maybe you mean the semtech-loramac package in RIOT ? Well, I’m still maintaining it as it is and it works. Several regions are supported, I use it my course, it’s now also used in the Mooc. But yes it needs some update and I know its drawbacks. Someone in the community willing to give a hand ? You could start by having a look at this 2 years old PR.
Regarding the in-house RIOT gnrc_lorawan implementation, I always thought it was a bad idea from the start to integrate it directly into RIOT rather than provide it as an external package (and I shared this thought with @jia200x, so this is not a surprise). Imagine if this stack was portable and usable on more than a single OS. Let’s imagine one second if the communities from FreeRTOS or Zephyr (that are way larger now than the RIOT one) could also use it. This stack would have certainly gained more external contributions, more features (regions) and wouldn’t be maintained by a one or two people (just think of the bus factor). Maybe this stack could also be promoted by the LoRa Alliance.