I would think that pure-storage NAS or network equipment
was effectively completely immune to local privilege escalation. I'll give you the NAS where it might be running untrusted containers or such, but that's it.
FreeBSD was the reason I chose TrueNAS Core. Unfortunately, you are right, TrueNAS Scale (Linux) is where they are focusing all their attention.
At this point I will not purchase additional TrueNAS equipment as I feel I was "rug pulled." I get that they are going after more of the Docker container/app market, but I just want a solid ZFS w/excellent networking NAS device. Linux is close to this ideal, but it isn't as "Set and Forget" as FreeBSD (IMO).
PlayStation 4 was a fork of FreeBSD 9, and is immune to this bug introduced in 14. Sony also changes a LOT, I'm not sure anything dealing with unix credentials even exists in this fork. It's not clear how much FreeBSD is even used in PlayStation 5 (2020), but it would be based off 12 or earlier (also immune to this bug from 14) (13 was released in 2021).
Whilst all are "soft-moddable" via HEN, a large number of the Slim and Superslims are not compatible with full custom firmware. Recently a hardware based exploit 'badWDSD' released which allow CFW, although even still a small number of Superslims are not compatible.