yeah, "shutdown -r now" also stopped working in 26.04, because either you're a regular user without privileges to do so, or you're root *but your TTY under your real UID* is used as an excuse to prevent you.
Either way, you're left to use systemctl with weird arguments (like there's any other fucking way to use systemctl) to restart your system from the command line, because shutdown has been unceremoniously made useless without actually being removed.