Last week I tried to install Ulauncher into a Linux Mint 21 freshly installed.

After installing Ulauncher using:

sudo add-apt-repository ppa:agornostal/ulauncher && sudo apt update && sudo apt install ulauncher

I got this error: «Warning apt-key is deprecated«.

After some Googling, I found this that help me to fix it.

Fixing process:

$ sudo apt-key list

Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
/etc/apt/trusted.gpg
--------------------
pub   rsa4096 2015-04-25 [SC]
      59EB DE77 2980 C381 CA13  FA59 FAF1 0206 9950 3176
uid           [ unknown] Launchpad PPA for Aleksandr Gornostal

...

Now, we need to remember the last 8 Hexa digits (99503176) of the corresponding app key.

$ sudo apt-key export 99503176 | sudo gpg --dearmour -o /usr/share/keyrings/ulauncher-archive.keyring.gpg

Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).

/etc/apt/sources.list.d$ ls

agornostal-ulauncher-jammy.list  official-package-repositories.list

We need to add an extra parameter to the deb line.

/etc/apt/sources.list.d$ sudo agornostal-ulauncher-jammy.list

#Previous deb line before the modification. 
#deb http://ppa.launchpad.net/agornostal/ulauncher/ubuntu jammy main

deb [signed-by=/usr/share/keyrings/ulauncher-archive.keyring.gpg] http://ppa.launchpad.net/agornostal/ulauncher/ubuntu jammy main

# deb-src http://ppa.launchpad.net/agornostal/ulauncher/ubuntu jammy main

/etc/apt/sources.list.d$ sudo apt update

Obj:1 http://ftp.caliu.cat/pub/distribucions/ubuntu/archive jammy InRelease
Obj:2 http://ftp.caliu.cat/pub/distribucions/ubuntu/archive jammy-updates InRelease                                                                      
Obj:3 http://ftp.caliu.cat/pub/distribucions/ubuntu/archive jammy-backports InRelease                                                                    
Bai:4 http://security.ubuntu.com/ubuntu jammy-security InRelease [110 kB]                                                                                
Ign:5 https://mirror.airenetworks.es/linuxmint/packages vanessa InRelease                                                                                
Obj:6 https://mirror.airenetworks.es/linuxmint/packages vanessa Release                                                                                
Obj:7 http://ppa.launchpad.net/agornostal/ulauncher/ubuntu jammy InRelease
Bai:9 http://security.ubuntu.com/ubuntu jammy-security/main amd64 DEP-11 Metadata [13,1 kB]
Bai:10 http://security.ubuntu.com/ubuntu jammy-security/universe amd64 DEP-11 Metadata [12,1 kB]
S'ha baixat 136 kB en 1s (265 kB/s)          
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apt mint ubuntu