Can't install qgis-plugin-grass in Ubuntu 20.04

[florisvdh]

After a fresh install of the current stable QGIS and GRASS on Ubuntu 20.04, it seems that I cannot install the qgis-plugin-grass package because it requires the non-existant dependency grass782.

$ export LANGUAGE=en_US:en
$ apt install qgis-plugin-grass 
[sudo] password for floris: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 qgis-plugin-grass : Depends: grass782
E: Unable to correct problems, you have held broken packages.

I have following repositories enabled:

deb [arch=amd64] https://qgis.org/ubuntu focal main

ppa:ubuntugis/ubuntugis-unstable

I could install packages qgis and grass without problems.

$ apt policy qgis
qgis:
  Installed: 1:3.14.15+32focal
  Candidate: 1:3.14.15+32focal
  Version table:
 *** 1:3.14.15+32focal 500
        500 https://qgis.org/ubuntu focal/main amd64 Packages
        100 /var/lib/dpkg/status
     3.10.5+dfsg-1~focal1 500
        500 http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu focal/main amd64 Packages
     3.10.4+dfsg-1ubuntu2 500
        500 http://ftp.belnet.be/ubuntu focal/universe amd64 Packages
$ apt policy grass
grass:
  Installed: 7.8.3-1~focal1
  Candidate: 7.8.3-1~focal1
  Version table:
 *** 7.8.3-1~focal1 500
        500 http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu focal/main amd64 Packages
        500 http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu focal/main i386 Packages
        100 /var/lib/dpkg/status
     7.8.2-1build3 500
        500 http://ftp.belnet.be/ubuntu focal/universe amd64 Packages
        500 http://ftp.belnet.be/ubuntu focal/universe i386 Packages

[gioman]

deb [arch=amd64] https://qgis.org/ubuntu focal main

ppa:ubuntugis/ubuntugis-unstable

@florisvdh if you use ubuntugis then you must use https://qgis.org/ubuntugis

[florisvdh]

Thanks for the hint. Note that your advice is not yet an option: Focal QGIS packages are still absent from https://qgis.org/ubuntugis (contrary to Bionic), while they are present only in https://qgis.org/ubuntu.

On the other hand the GRASS website's 'quick link' points to ppa:ubuntugis/ubuntugis-unstable for installation of GRASS on Ubuntu (i.e. including Focal). There, it is at 7.8.3 (for Focal and older). In the Ubuntu Focal universe repository, GRASS is at 7.8.2. Removing the PPA and re-installing GRASS from Ubuntu Focal solved the problem.

IMHO it would be nice if GRASS would point at the requirement for GRASS to be installed from a repository, compatible with the one holding qgis-plugin-grass, if the latter is to be installed. In the case of Ubuntu Focal this is not the ubuntugis-unstable PPA (yet). Suggestion @neteler

Actually not installing GRASS directly but only following the recommendations at https://qgis.org/en/site/forusers/alldownloads.html#debian-ubuntu to do sudo apt install qgis qgis-plugin-grass would work and install the compatible version of GRASS, provided that no conflicting repositories are activated (cf. the recommendation: "Please remove all the QGIS and GRASS packages you may have installed from other repositories before doing the update."). However this would not yet install grass-doc and grass-gui, so to install GRASS one still would be guided towards the PPA following the GRASS website.

[Matesanz]

deb [arch=amd64] https://qgis.org/ubuntu focal main

ppa:ubuntugis/ubuntugis-unstable

@florisvdh if you use ubuntugis then you must use https://qgis.org/ubuntugis

🎉 That fixed my issue.
To those wondering what @florisvdh means by using ubuntugis:

🛑 instead of:

sudo add-apt-repository "deb https://qgis.org/ubuntu $(lsb_release -c -s) main"

✔️ use:

sudo add-apt-repository "deb https://qgis.org/ubuntugis $(lsb_release -c -s) main"

[Andres-GM96]

deb [arch=amd64] https://qgis.org/ubuntu focal main

ppa:ubuntugis/ubuntugis-unstable

@florisvdh if you use ubuntugis then you must use https://qgis.org/ubuntugis

tada That fixed my issue.
To those wondering what @florisvdh means by using ubuntugis:

stop_sign instead of:

sudo add-apt-repository "deb https://qgis.org/ubuntu $(lsb_release -c -s) main"

heavy_check_mark use:

sudo add-apt-repository "deb https://qgis.org/ubuntugis $(lsb_release -c -s) main"

This works for me 👯‍♂️

[Robinlovelace]

Additional update from me: this fixed the issue for me also 🎉

sudo add-apt-repository "deb https://qgis.org/ubuntugis $(lsb_release -c -s) main"

Great to see you putting in great contributions in the R and QGIS communities @florisvdh !

[VictorCarreira]

E: The repository 'https://qgis.org/debian your-distributions-codename Release' does not have a Release file.

how to remove it from the source list if does it not appears?

[jef-n]

E: The repository 'https://qgis.org/debian your-distributions-codename Release' does not have a Release file.

your-distributions-codename is to be replaced with your distribution's codename.

[VictorCarreira]

Thanks for the reply, but didn't work for me.
But I've tried to remove it by accessing '/etc/apt/sources.list.d' as root and removing manually the 'qgis.sources' in the terminal.
That worked.

Now sudo apt update is clean once again.