A remote is a URL location of a repository. A local git repo can point to multiple remotes by using the git remote <opts> functionality. For instance, you can point your local repo to GitHub, GitLab, and BitBucket and choose which to push to using the command git push <branch> <remote>.
In the past we have tons of hosters so we can easily spread our code in many "mirror", now there is GitHub and few others, mostly on the very same "cloud".
I mean you have no damn viable remote. Single devs can share code P2P but nothing that can work instantly out of the box.
In the context of the original comment, think: "setup a /second/ remote" as the meaning. If the first 'remote' is github, the second remote could be gitlab, and so forth.
Sorry for being rude but for me is unacceptable to depend on tons of proprietary stuff from a handful of vendors. Even personal websites that use Google Fonts, some JS framework directly from the "project" CDN (too hard to keep it on your disk, up to date) etc...
We need to be interdependent or independent not dependent of few subjects that make money on us for witch us are puppets. How can we say "it's FOSS" if so? How can we have FOSS as the tip of a proprietary iceberg?
One can, if one chooses, setup a git repository on a spare PC in ones basement and have a "git repository" into which one or more collaborators can "git push" and "git pull" to/from.
In the context of the original post, to which you asked "what is another remote", the second (or third, or fourth) 'remote' can be "any git repository to which the individual has access".
Having a second remote does not, in an of itself, require that that second remote be one of the proprietary git hosting systems, nor require that it be one of the semi-proprietary or open source hosting systems. It could just as well be plain git running in repository serving mode on an old PC.
See the documentation for the "git http-backend" and "git daemon" commands that are built into the git distribution.
now with GitHub&c excluding Savannah the sole friendly option is buy a domain, a VPS and host there the project...
That's the problem, not technical but "political" to a certain extent.
In the past someone try GitTorrent to solve this problem a bit (opening the door for "personal hosting at home" but it's a dead project now ad it was never completed. Mostly because newcomers think GitHub&c as a free space by nature, something guarantee to work always and been always free without any other "occult" cost.
When I was a bit younger I read that "internet" was a fantastic decentralized infrastructure explicitly design to being fault-tolerant and unlockable as possible to survive any critical scenario... Now it seems more a deep substrate of a modern mainframe... So deep that only few subject can really access it, all others are in their own hand...