TL;DR having gotten Pomerium working the way I wanted on my Synology a number of years ago in front of a set of Docker containers, I’m going to be repeating this on TrueNAS Scale which is k3s-based.
Long time user, first time caller. My venerable DS918+ (and DX517) is showing its age and lack of capacity, so I recently impulse-purchased a SER6 Pro (AMD platform NUC-like with 32GB of DDR5). I started with Proxmox, then TrueNAS, and now TrueNAS Scale. During that multi-step process, I gained a new appreciation for the job Synology does making an appliance out of a complex problem. (I am going to swap in Harbormaster someday instead of Portainer, tho…)
TrueNAS Scale has a built-in ingress which I’ve disabled and replaced with MetalLB and Traefik as part of TrueCharts, which appears to be what power users do. TrueCharts recommends Authelia + LLDAP + Traefik and while I’m sure that stack is lovely it doesn’t get me what I had with Pomerium.
Posting this in case folks have recommendations or links; my ultimate goal is to get Pomerium as part of upstream TrueCharts. (Note that TrueNAS Scale is very different vs. regular TrueNAS - it’s Linux, not BSD.) Time to read pomerium traefik auth proxy and start breaking things 
