Emacs 26.1 as packaged in Debian buster.
M-x package-list-packages I can select any package from the MELPA repo https://melpa.org/packages/ and then install it. But when I try to get any package from the GNU ELPA repo https://elpa.gnu.org/packages/ I get an error:
Contacting host: elpa.gnu.org:443 package-install-from-archive: https://elpa.gnu.org/packages/ack-1.8.tar: Bad Request
And of course I get the same error if I try to install it directly, outside the package menu with
M-x package-install <RET> ack.
When I browse
elpa.gnu.org with Firefox I can download the file just fine, and I can also download it directly from the command line with
curl -L -O https://elpa.gnu.org/packages/ack-1.8.tar
Update: I found https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=942413 . But I checked and I already have the latest signing key in
~/.emacs.d/elpa/gnupg , namely
066DAFCB81E42C40. So my problem must be different.