I have commented about this in the past. According to iFi, the zen streaming software is based on Volumio (version 2). This in turn is based on Debian Jessie (a variety of Linux), which officially lost support in 2020. I don't mind that the operating system software for the Zen hardware is outdated, and acknowledge that iFi has made substantial improvements in terms of audio. However, since they have stated that they aren't ready to support Volumio 3 (based on Debian Buster), I would appreciate hearing that they are aware of and actively addressing any known security issues associated with their software. (This is something audio companies in this market rarely do.) I don't know the outlook for future support for other decives in the audio chain, but in principle, iFi could provide patches for changes in things like NAA service from HQPlayer...
(See the links below for info about Debian Jessie.)
https://www.debian.org/News/2020/20200709
https://www.dogsbody.com/blog/debian-8-jessie-eol-30th-june-2020/The comment I made comes from the Roon forum. In the forum one of the users said:
"I hope iFi would update the NAA to the latest version at some point. I hope it could fix the problem when ZS loses the DAC USB-input if DAC is switched on/off or inputs changed." To which one user replied:
"This is not possible because it would be necessary to upgrade the OS to a Debian version more recent than the very old Jessie (and the kernel, the libraries, etc)."
I would like to be able to upgrade to future versions of NAA, and would not be happy if I am not able to do so because of limitations in the linux kernel used.