Solved How do I install packages on old versions?

I have an old machine (10.4-RELEASE) and I need to install Python 3.8 on it.

This is my pkg.conf file:
FreeBSD: {
  url: "pkg+${ABI}/quarterly",
  mirror_type: "srv",
  signature_type: "fingerprints",
  fingerprints: "/usr/share/keys/pkg",
  enabled: yes

This is what I get when I try to update the repository:
# pkg update
Updating FreeBSD repository catalogue...
pkg: repository meta /var/db/pkg/FreeBSD.meta has wrong version 2
pkg: Repository FreeBSD load error: meta cannot be loaded No error: 0
pkg: Not Found
repository FreeBSD has no meta file, using default settings
pkg: Not Found
Unable to update repository FreeBSD
Error updating repositories!

I know it is an old version and the repository has been offline for a long while, but I'd like to know if there is a way.
You would have to build the package yourself. All the repositories overwrite old packages, they don't keep a backlog.
FreeBSD 10.4 has been end-of-life (and thus not supported any more) since October 31, 2018.

Why do you need to keep that old version?
<> for latest included python36-3.6.4.txz however I should not assume that it'll work as expected. At least, it doesn't fit your 3.8 requirement.
I guess that was just what I was looking for. Thank you very much. I'll keep that in mind for future reference.

I had to replicate the pool manually. I already took the old machine offline. Sometimes toiling has its benefits too, you know; you learn new things along the way.
How would I do that?

How would I do that?

You use git to check out a version of the ports tree that is roughly the right timeframe for 10.4. Then you cd into the appropriate ports directory and do `make install` and `make package` if you want to keep binary packages.

You will probably have to retrieve a few distfiles manually.