We’re still supporting and occasionally updating the glue code between LXD/LXC and CRIU but we no longer have a full-time engineer working on CRIU.
Our goal at the time was to get CRIU to work with most common workloads on modern distributions (at the time Ubuntu 16.04 LTS). This turned into a bit of a losing battle as every time we’d add support for some new kernel feature in CRIU, the upstream Linux kernel would grow support for a dozen more features that CRIU didn’t understand.
So CRIU is certainly viable for very specific environments where the user is in complete control of the workload and distribution they run it on, but that market isn’t sufficient for us to justify very costly engineering efforts.
So right now, we tend to redirect requests for missing CRIU features directly to upstream CRIU where there is an active community of contributors that eventually tackle the most common limitations. There is a fair amount of investment in CRIU coming from academia, HPC and some big organizations like Google also actively make use of it and contribute fixes to it.
So it’s certainly not a dead end but for us as a generic container tool that focuses on generic workloads on modern distros, it’s not a current focus.