[root@freebsd15 ~]# zpool upgrade zroot
This system supports ZFS pool feature flags.

Enabled the following features on 'zroot':
  redaction_list_spill
  raidz_expansion
  fast_dedup
  longname
  large_microzap
  block_cloning_endian
  physical_rewrite

Pool 'zroot' has the bootfs property set, you might need to update
the boot code. See gptzfsboot(8) and loader.efi(8) for details.

[root@freebsd15 ~]# gpart show
=>       40  488397088  diskid/DISK-50026B76843420B6  GPT  (233G)
         40       1024                             1  freebsd-boot  (512K)
       1064        984                                - free -  (492K)
       2048    4194304                             2  freebsd-swap  (2.0G)
    4196352  484200448                             3  freebsd-zfs  (231G)
  488396800        328                                - free -  (164K)

[root@freebsd15 ~]# gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 diskid/DISK-50026B76843420B6
partcode written to diskid/DISK-50026B76843420B6p1
bootcode written to diskid/DISK-50026B76843420B6

[root@freebsd15 ~]# gpart status
                          Name  Status  Components
diskid/DISK-50026B76843420B6p1      OK  diskid/DISK-50026B76843420B6
diskid/DISK-50026B76843420B6p2      OK  diskid/DISK-50026B76843420B6
diskid/DISK-50026B76843420B6p3      OK  diskid/DISK-50026B76843420B6