Hello @kittonian,
certbot-auto has been deprecated and now it isn't supported in any system so if you want to use it you can do it but it won't be updated.
Regarding the certbot package included in your distribution... I don't think it's worth to install it because I'm pretty sure the version would be outdated so you will be really downgrading it and if you are using a legacy Debian I also suppose you won't get any update.
As certbot is now being distributed as a snap package you could install it but snap is not available in versions prior to Debian 9 so if your are using Debian 7 or 8 you can't go ahead.
My advice, use another client like acme.sh (it is a bash shell script and has minimum requirements but it is full of features). Yes, you will have to learn how to use it and migrate your stuff but you will get an updated client that works on your legacy system.
Good luck,
sahsanu