lavamaster@lavamaster:~$ sudo apt update
Hit:1 http://deb.debian.org/debian buster InRelease
Get:2 http://security.debian.org/debian-security buster/updates InRelease [65.4 kB]               
Get:3 http://deb.debian.org/debian buster-updates InRelease [51.9 kB]                                                             
Get:4 http://deb.debian.org/debian buster-backports InRelease [46.7 kB]                                                                    
Ign:5 https://apt.lavasoftware.org/daily buster InRelease                                                 
Err:6 https://apt.lavasoftware.org/daily buster Release                    
  Certificate verification failed: The certificate is NOT trusted. The certificate issuer is unknown.  Could not handshake: Error in the certificate verification. [IP: 51.148.40.41 443]
Get:7 http://ftp.debian.org/debian stretch-backports InRelease [91.8 kB]
Reading package lists... Done      
E: The repository 'https://apt.lavasoftware.org/daily buster 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.
lavamaster@lavamaster:~$