It should be there for the Web UI at manage.alta.inc at least. See if you can find it as per below.
S8 Switch (and perhaps S16/S24 as well?!):
Network → S8 Switch device → Settings → Advanced (at the bottom) → Reboot (at the very bottom)
Route10:
Network → Route10 device → Advanced (at the bottom) → Reboot (at the very bottom)
AP6 Pro:
Network → AP6 Pro device → Settings → Advanced (at the bottom) → Reboot (at the very bottom)
