Another user reported a similar problem with Wifi last year, with an odd solution
similar network devices and Wifi would fail after reboot
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controll
er (rev 15)
05:00.0 Network controller: **Realtek Semiconductor Co., Ltd. RTL8723DE 802.11b/g/n** PCIe Adapter
Replacing the NIC driver r8169 with r8168 driver resolved issues with RTL8723DE Wifi
Odd problem with WiFi: stops working after reboot
so I suggest installing r8168 driver
sudo mhwd -i pci network-r8168
Or use Manjaro Settings Manager > Hardware Configuration
Internet slower on KDE
Manjaro Settings Manager/mhwd should install the r8168 driver and kernel headers packages and blacklist the r8169 driver