I am sure, that I am missing something very trivial and obvious, but I failed to get it.
Debugger entered--Lisp error: (error "Location https//elpa.gnu.org/packages/ is not a url nor an absolute file name")
signal(error ("Location https//elpa.gnu.org/packages/ is not a url nor an absolute file name"))
package--with-response-buffer-1("https//elpa.gnu.org/packages/" #f(compiled-function () #<bytecode 0x15f5309650fab0c5>) :file "archive-contents" :async nil :error-func$
package--download-one-archive(("elpa" . "https//elpa.gnu.org/packages/") "archive-contents" nil)
package--download-and-read-archives(nil)
package-refresh-contents()
funcall-interactively(package-refresh-contents)
call-interactively(package-refresh-contents record nil)
command-execute(package-refresh-contents record)
execute-extended-command(nil "package-refresh-contents" "package-re")
funcall-interactively(execute-extended-command nil "package-refresh-contents" "package-re")
call-interactively(execute-extended-command nil nil)
command-execute(execute-extended-command)