slow snap store connection

I googled around for a while and I basically found nothing on how to create a snap store mirror.

Did you upgrade to 18.10 in between (if you upgraded online) or did you wipe 18.04 off and do a clean install of 19.04 (why you'd leave the LTS is a weird one)

19.04 is only supported a short while. You may want to upgrade to 19.10
https://wiki.ubuntu.com/Releases

ADSL is fast enough for home use and is what provides the majority of home broadband here in the UK. We wake up in the times of ADSL daily. Same in China.....It's not slow.

https://docs.ubuntu.com/snap-store-proxy/en/install
https://snapcraft.io/snap-store-proxy

Found that in about 30 seconds.....

mirror, not proxy.
well... what I want to say by mentioning ADSL.. is that I want to say that its really slow...
snap install [anything] needs snap install core, right?
what I'm really looking for is something equivalent to /etc/apt/sources.list

I get something like "you need to run apt --fix-broken install" after upgrading and when I tried to install or upgrade anything, and apt--fix-broken install wants to snap install lxd, which leads to snap install core, while I can't do anything but to watch it download at the speed of a snail.

[from 18.04]
do-release-upgrade
Ctrl+C when installing lxd (I suspected that it hanged)
apt update; apt upgrade -> needs --fix-broken install
"hanged" when snap install lxd>snap install core
opened up a screen session and snap install lxd
went to sleep
[morning]
apt upgrade worked fine

I couldn't use a proxy because I can install nothing without installing the core, but on debian apt has /etc/apt/sources.list so I can update/install from another source.

I don't understand how:

"but on debian apt has /etc/apt/sources.list so I can update/install from another source."

You can install from any source you can add, you can even install from packages on your local drive(s).... What do you mean please?

there are some mirror sites that syncs with the main site periodically, like https://mirrors.ocf.berkeley.edu, and https://mirrors.tuna.tsinghua.edu.cn
I can find instructions on how to mirror a repository like https://help.ubuntu.com/community/Rsyncmirror and https://wiki.archlinux.org/index.php/mirrors

I can't find them for snap store.
maybe I missed something?

btw, 19.04 upgraded to 19.10 smoothly.
I left LTS because... I simply wanted to (lol
The cloud service provider gives 18.04 by default.

Was it OK in the LTS. The non LTS releases are very short supported

it's not at all related to LTS or not...
It's about designing....
I'm closing this anyway, seems that I'm not getting any closer to a solution.

just google, "ubuntu snap mirror"