The main repository was missing.

defaults/main.yml

@@ -11,6 +11,9 @@
 #
 # Set to True if you want install from the CRAN deb repository
 r_install_cran_repo: False
+# This si the CRAN main repository, that contains the r-base-* packages
+r_cran_ubuntu_repo_key: 'E298A3A825C0D65DFD57CBB651716619E084DAB9'
+r_cran_ubuntu_repo: 'deb https://cloud.r-project.org/bin/linux/ubuntu $(lsb_release -cs)-cran40/'
 # Use 'marutter/c2d4u3.5' for R 3.6
 r_cran_ubuntu_packages_ppa_trusty: 'ppa:marutter/c2d4u'
 # 4.1, Ubuntu 18.04+

tasks/r-installation-deb.yml

@@ -19,6 +19,17 @@
   tags: [ 'r_software', 'r_repo' ]
 
 - block:
+  - name: Install the CRAN main R repository key
+    apt_key:
+      keyserver: 'keyserver.ubuntu.com'
+      id: '{{ r_cran_ubuntu_repo_key }}'
+
+  - name: Install the CRAN main R repository
+    apt_repository:
+      repo: '{{ r_cran_ubuntu_repo }}'
+      state: present
+      update_cache: yes
+
   - name: Add the CRAN repository (Ubuntu Bionic PPA)
     apt_repository:
       repo: '{{ r_cran_ubuntu_packages_ppa }}'
@@ -38,12 +49,18 @@
   tags: [ 'r_software', 'r_repo' ]
 
 - block:
-  - name: Remove the CRAN repository
+  - name: Remove the CRAN repositores
     apt_repository:
       repo: '{{ r_cran_ubuntu_packages_ppa }}'
       state: absent
       update_cache: yes
 
+  - name: Remove the CRAN main repository
+    apt_repository:
+      repo: '{{ r_cran_ubuntu_repo }}'
+      state: absent
+      update_cache: yes
+
   when: not r_install_cran_repo
   tags: [ 'r_software', 'r_repo' ]