Sublime is the editor I am used to. I want to download it after reinstalling the system recently, but according to the download method on the official website, the following error will appear:

@ubuntu:~$ wget -qO - https://download.sublimetext.com/sublimehq-pub.gpg | sudo apt-key add -
OK
@ubuntu:~$ echo "deb https://download.sublimetext.com/ apt/stable/" | sudo tee /etc/apt/sources.list.d/sublime-text.list
deb https://download.sublimetext.com/ apt/stable/
@ubuntu:~$ sudo apt update && sudo apt install sublime-text
Hit:1 http://us.archive.ubuntu.com/ubuntu focal InRelease                      
Hit:2 http://security.ubuntu.com/ubuntu focal-security InRelease               
Hit:3 http://us.archive.ubuntu.com/ubuntu focal-updates InRelease              
Ign:4 https://download.sublimetext.com apt/stable/ InRelease                   
Hit:5 http://us.archive.ubuntu.com/ubuntu focal-backports InRelease            
Err:6 https://download.sublimetext.com apt/stable/ Release 
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate.  Could not handshake: Error in the certificate verification. [IP: 104.236.0.104 443]
Reading package lists... Done                             
E: The repository 'https://download.sublimetext.com apt/stable/ Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

The reason is that a software package called “ca-certificates” is not installed. After installation, you can execute the installation instruction of sublime from the beginning.

@ubuntu:~$ sudo apt install ca-certificates