FAILED! => {"changed": false, "msg": "apt cache update failed"} when trying to - ansible

Question

I am new to Ansible and try, as an example, a task to install Vivaldi. My only task in a role Vivaldi update starts with
- name: Run apt upgrade
apt:
upgrade: "yes"
update_cache: yes
cache_valid_time: 432000
- name: Add Vivaldi Repository
apt_repository:
repo: "deb https://repo.vivaldi.com/stable/deb/ stable main"
state: present
filename: vivaldi.list
update_cache: true
tags:
- vivaldi
And with this, I fail on localhost on a Debian 10 (Buster) installation:
Linux london 4.19.0-12-amd64 #1 SMP Debian 4.19.152-1 (2020-10-18) x86_64 GNU/Linux).
All commands succeed on the command line.
Ansible is 2.9.15.
The first task runs OK (if run alone), but the second fails with:
FAILED! => {"changed": false, "msg": "apt cache update failed"}.
A task to add a repository key fails with:
FAILED! => {"changed": false, "id": "6D3789EDC3401E12", "msg": "key does not seem to have been added"}
However, if I add the repository manually to /etc/apt/sources.list the last task,
- name: Install Vivaldi
apt:
name: vivaldi-stable
update_cache: yes
state: latest
tags:
- vivaldi
it succeeds.
What am I doing wrong?

Answer 1

According to official documentation you need to add the key and later the repository:
Manual setup of the Vivaldi Linux repositories
Edit your playbook with the task Add key:
- name: Run apt upgrade
apt:
upgrade: "yes"
update_cache: yes
cache_valid_time: 432000
- name: Add key
apt_key:
url: https://repo.vivaldi.com/archive/linux_signing_key.pub
state: present
tags:
- vivaldi
- name: Add Vivaldi Repository
apt_repository:
repo: "deb https://repo.vivaldi.com/stable/deb/ stable main"
state: present
filename: vivaldi.list
update_cache: true
tags:
- vivaldi
- name: Install Vivaldi
apt:
name: vivaldi-stable
update_cache: yes
state: latest
tags:
- vivaldi