Ubuntu 18.04升级至20.04后无网络连接且网络图标丢失的技术求助

最近我把Ubuntu桌面从18.04版本升级到了20.04，重启之后发现不仅网络连接彻底失效，就连右上角状态栏的网络图标也消失了。我已经谷歌搜索折腾了两天，还是没找到能解决问题的办法，希望能在这里得到大家的帮助。

下面是我运行的一些排查命令及对应的输出信息：

查看/etc/network/interfaces配置文件 #

执行命令：sudo gedit /etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)

auto lo

iface lo inet loopback

执行networkctl命令查看网络状态 #

执行命令：networkctl

WARNING: systemd-networkd is not running, output will be incomplete.

IDX LINK TYPE     OPERATIONAL SETUP

1 lo   loopback n/a         unmanaged

1 links listed.

执行ifconfig命令查看网络接口 #

执行命令：ifconfig

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536

inet 127.0.0.1  netmask 255.0.0.0

inet6 ::1  prefixlen 128  scopeid 0x10<host>

loop  txqueuelen 1000  (Local Loopback)

RX packets 4047  bytes 302018 (302.0 KB)

RX errors 0  dropped 0  overruns 0  frame 0

TX packets 4047  bytes 302018 (302.0 KB)

TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

执行ip ad命令查看网络接口详情 #

执行命令：ip ad

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo

valid_lft forever preferred_lft forever

inet6 ::1/128 scope host

valid_lft forever preferred_lft forever

执行lshw -C network命令查看网络硬件信息 #

执行命令：sudo lshw -C network

*-network UNCLAIMED

description: Network controller

product: RTL8188EE Wireless Network Adapter

vendor: Realtek Semiconductor Co., Ltd.

physical id: 0

bus info: pci@0000:01:00.0

version: 01

width: 64 bits

clock: 33MHz

capabilities: pm msi pciexpress cap_list

configuration: latency=0

resources: ioport:4000(size=256) memory:d1200000-d1203fff

*-network UNCLAIMED

description: Ethernet controller

product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller

vendor: Realtek Semiconductor Co., Ltd.

physical id: 0

bus info: pci@0000:02:00.0

version: 15

width: 64 bits

clock: 33MHz

capabilities: pm msi pciexpress msix bus_master cap_list

configuration: latency=0

resources: ioport:3000(size=256) memory:d1104000-d1104fff memory:d1100000-d1103fff

补充说明：我试过插网线和连WiFi两种方式，都无法正常上网，但同一网络下的其他设备都能正常使用网络。我现在完全摸不着头绪，恳请各位大佬帮忙分析一下问题所在，给出解决建议！

备注：内容来源于stack exchange，提问作者ash