It’s not the cleanest way to do it I guess, but I had the same problem as you and I changed:
$ sudo add-apt-repository \
"deb [arch=amd64] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) \
stable"
to
$ sudo add-apt-repository \
"deb [arch=amd64] https://download.docker.com/linux/ubuntu \
bionic \
stable"
because
$(lsb_release -cs)
returns “eoan” (the name of the latest ubuntu version, currently 19.10) and it seems to cause problems.
Replacing this with “bionic” (ubuntu 18.10) worked perfectly for me, and I still have no problems 4 months later.
Don’t forget to open “/etc/apt/sources.list” and comment-out/delete the line:
deb-src [arch=amd64] https://download.docker.com/linux/ubuntu eoan stable
to avoid conflicts.
(You added this with the first command you entered in this process.)