@Simran Singh Sincere apologies for the long delay and thanks for your time and patience for an update on this query.
We have checked this with our internal teams and below is an update regarding installation of ADU agent on NixOS.
Currently this is not on our roadmap. Our team is prioritizing other more common distros at this time.
I suggest you, please create a feedback item here and upvote for this feature request.
Hope this helps. Do let us know if you have any further queries.
If the response is helpful, please click "Accept Answer" and upvote it.