Error connecting to new system - 400 OK - Got 401 (Truecommand + Traefik?)

[underpickled]

Initial conditions:

• TrueNAS Scale 23.10.2 (latest as of this posting)
• Traefik running, properly routing (UI ports changed to 81/444, Traefik is set for 80/443)
• Can access UI via https://sub.domain.net/
• Added truecommand app on the same system (yes, I know, I just want to try it out) with Traefik ingress to sub2.domain.net
• Can access truecommand UI through sub2.domain.net
• I created an API key in the TrueNAS UI

Problem:

• I add a new system with the hostname sub.domain.net, port 443, and the API key
• I get this error
  
  

Any tips appreciated. My goal is not to forward any ports except for 80/443 and have Traefik manage all ingress. I've been able to do this with apps and external services, but something funky is happening in this case.