I was going through the add-ons sections looking for specific .xpi files and I was wondering if there was a site (like that of the legacy firefox ftp) where you could theoretically download every plugin ever made for firefox. It seems a shame to have mirrors of firefox without the added benefits of the plugins that took (compilatively speaking) thousands of years of development and many add-ons for firefox that are legacy cannot be found for legacy firefox but I’m sure they are on a server somewhere like legacy apple software. If there isn’t one that people can access, it would be my suggestion as a part time developer to create one for people who care about legacy abandonware like me.
There is this small list of curated XPI files that you can probably use (or improve) : https://github.com/TarekJor/Firefox-52-ESR-legacy-addon
I was thinking more along these lines: https://ftp.mozilla.org/pub/firefox/releases/
If something like this doesn’t exist yet, I think it requires the attention of someone with more authority than myself or most Firefox moderation. I’m not sure how the rest of the community feels about it but I am all for the abandonware movement and would love to see this move forward.
There are such projects out there, like https://github.com/JustOff/ca-archive or a mirroring tool mentioned in this mailinglist thread: https://mail.mozilla.org/pipermail/dev-addons/2017-August/003033.html
Also mentioned on those threads, there’s an API. However, legacy add-ons will be disabled later this year, so they won’t be available anymore.