Comment 7 for bug 1975576

I've tested netplan.io 0.104-0ubuntu2~20.04.2 from focal-proposed. The test plan passed.

root@ff-nm:/x# apt list *netplan*
Listing... Done
libnetplan-dev/now 0.104-0ubuntu2~20.04.2 amd64 [installed,local]
libnetplan0/now 0.104-0ubuntu2~20.04.2 amd64 [installed,local]
netplan.io/now 0.104-0ubuntu2~20.04.2 amd64 [installed,local]

root@ff-nm:/x# sudo nmcli c add con-name test3 type wifi ssid ubuntu-wpa2-wpa3-mixed ifname wlan0
Connection 'test3' (a97b1974-3a53-49c6-87e7-84cf692d7f5c) successfully added.

root@ff-nm:/x# sudo nmcli c modify test3 wifi-sec.key-mgmt sae wifi-sec.psk test1234

root@ff-nm:/x# nmcli c show test3 --show-secrets | egrep "wireless-security.(key-mgmt|psk)"
802-11-wireless-security.key-mgmt: sae
802-11-wireless-security.psk: test1234
802-11-wireless-security.psk-flags: 0 (none)

root@ff-nm:/x# netplan get | grep password
            password: "test1234"
root@ff-nm:/x# netplan get | grep key-mgmt
              wifi-security.key-mgmt: "sae"

root@ff-nm:/x# netplan get wifis.NM-a97b1974-3a53-49c6-87e7-84cf692d7f5c
renderer: NetworkManager
match:
  name: "wlan0"
dhcp4: true
dhcp6: true
ipv6-address-generation: "stable-privacy"
access-points:
  "ubuntu-wpa2-wpa3-mixed":
    auth:
      key-management: "none"
      password: "test1234"
    networkmanager:
      uuid: "a97b1974-3a53-49c6-87e7-84cf692d7f5c"
      name: "test3"
      passthrough:
        connection.permissions: ""
        wifi.mac-address-blacklist: ""
        wifi-security.key-mgmt: "sae"
        ipv4.dns-search: ""
        ipv6.dns-search: ""
        ipv6.ip6-privacy: "-1"
        proxy._: ""
networkmanager:
  uuid: "a97b1974-3a53-49c6-87e7-84cf692d7f5c"
  name: "test3"