0bda:d723 Realtek Semiconductor Corp. 802.11n WLAN Adapter not works in Ubuntu 20.04

Since you have tried several other drivers previously, this assumes that you have installed all of the prerequisites.

With a working internet connection by ethernet, tethering or whatever means possible, open a terminal and do:

git clone https://github.com/lwfinger/rtw88.git
cd rtw88
make
sudo make install
sudo modprobe rtw_8723de

You will need to disable Secure Boot.

This driver must be reinstalled every time that Update Manager offers a newer kernel version. After the requested reboot, with a temporary internet connection by ethernet, tethering or whatever means possible, do:

cd rtw88
make clean
git pull
make
sudo make install
sudo modprobe rtw_8723de

Your wireless should be working again. Please retain the rtw88 file and these instructions for that time.