works
❯ sudo pacman-mirrors --api --set-branch stable --proto https --country Germany
::INFO Branch in config is changed
::INFO Protocols in config is changed
::INFO Downloading mirrors from Manjaro
::INFO => Mirror pool: https://repo.manjaro.org/mirrors.json
::INFO => Mirror status: https://repo.manjaro.org/status.json
::INFO User generated mirror list
::------------------------------------------------------------
::INFO Custom mirror file saved: /var/lib/pacman-mirrors/custom-mirrors.json
::INFO Using custom mirror file
::INFO Querying mirrors - This may take some time
0.423 Germany : https://mirror.alpix.eu/manjaro/
0.498 Germany : https://ftp.gwdg.de/pub/linux/manjaro/
0.380 Germany : https://mirror.23m.com/manjaro/
0.465 Germany : https://ftp.halifax.rwth-aachen.de/manjaro/
0.388 Germany : https://mirror.netcologne.de/manjaro/
0.337 Germany : https://manjaro.moson.eu/
0.418 Germany : https://mirror.moson.org/manjaro/
::INFO Writing mirror list
::Germany : https://manjaro.moson.eu/stable/$repo/$arch
::Germany : https://mirror.23m.com/manjaro/stable/$repo/$arch
::Germany : https://mirror.netcologne.de/manjaro/stable/$repo/$arch
::Germany : https://mirror.moson.org/manjaro/stable/$repo/$arch
::Germany : https://mirror.alpix.eu/manjaro/stable/$repo/$arch
::Germany : https://ftp.halifax.rwth-aachen.de/manjaro/stable/$repo/$arch
::Germany : https://ftp.gwdg.de/pub/linux/manjaro/stable/$repo/$arch
::INFO Mirror list generated and saved to: /etc/pacman.d/mirrorlist
::INFO To reset custom mirrorlist 'sudo pacman-mirrors -id'
::INFO To remove custom config run 'sudo pacman-mirrors -c all'