backportpackage: Invalid URL [...] No host supplied (wrong https:/ schema)

Maybe add an extra slash or maybe even 2

user@hp-laptop:~$ backportpackage -d jammy -u ppa:readableauthor/ppa https:///mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc
Invalid URL 'https:/mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc': No host supplied
user@hp-laptop:~$ backportpackage -d jammy -u ppa:readableauthor/ppa https:////mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc
Invalid URL 'https:/mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc': No host supplied

Maybe you need to remove "https://"...?

Likely not

user@hp-laptop:~$ backportpackage -d jammy -u ppa:readableauthor/ppa mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc
Parsed mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc as /home/user/mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc
Source file /home/user/mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc not found

Have you tried downloading the *.dsc, *.orig.tar.gz and *.debian.tar.xz files to your local hard disk and starting the backportpackage command without reference to the mxrepo server URL but simply with the local file name?

I may try it later, but I'm more interested in URL capability (it's much less labor-intensive). It seems like my use case fails because of some bug. If someone can confirm, I'd just post is as such.

Try putting quotes around the url, and if that does not work either, then this probably deserves being reported as bug.

user@hp-laptop:~$ backportpackage -d jammy -u ppa:readableauthor/ppa "https://mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc"
Invalid URL 'https:/mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc': No host supplied

Linked related bug

The URL you are using [for the PPA] is a repository address for MX Linux-19 O. S. not Ubuntu.
Ubuntu-dev-tools is in Ubuntu's Repository[universe]
https://packages.ubuntu.com/jammy/ubuntu-dev-tools

Yes, I'm trying to make a backport from MX to Ubuntu. My ubuntu-dev-tools is from Ubuntu 22.04.1 install

Ubuntu has built the most current available package: ubuntu-dev-tools (0.189)
Debian is using: ubuntu-dev-tools (0.183)
MX Linux is using the same package as Debian.
I suggest using Ubuntu's packaging.

Yes I'm using 0.189 from jammy

To finish the confusion about versions, what is the output of the following diagnostic commands:

uname -a
lsb_release -crid
apt policy ubuntu-dev-tools

And as additional tests:

Does the command work or fail, when you replace "https:" by "http:"?

Does the command work or fail with local files?

user@hp-laptop:~$ uname -a
Linux hp-laptop 5.15.0-52-generic #58-Ubuntu SMP Thu Oct 13 08:03:55 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

user@hp-laptop:~$ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 22.04.1 LTS
Release: 22.04
Codename: jammy
user@hp-laptop:~$ apt policy ubuntu-dev-tools
ubuntu-dev-tools:
  Installed: 0.189
  Candidate: 0.189
  Version table:
 *** 0.189 500
        500 http://us.archive.ubuntu.com/ubuntu jammy/universe amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu jammy/universe i386 Packages
        100 /var/lib/dpkg/status

user@hp-laptop:~$ backportpackage -d jammy -u ppa:readableauthor/ppa http://mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc
Invalid URL 'http:/mxrepo.com/mx/repo/pool/main/i/i-nex/i-nex_7.6.0-0.1~mx19+1.dsc': No host supplied

http:// didn't work. Local files work. (I'm interested in URL backporting)

You are running Ubuntu and the Ubuntu-provided version of ubuntu-dev-tools, etc,. so your question and the bug report seem fully valid to me.

Eventually you could try debugging the program (with pdb3).

I doubt I'd manage pdb3 to be honest