In 2015 we started migrating repositories from SVN to GitHub
I feel compelled to point out, for the benefit of anyone who might be reading this without knowing about such things, that Git is not the same thing as Github. You can (and should, especially if you’re a big-time tech company with the resources to host your own repo and some respect for free software) choose to have all the convenient features of Git without going anywhere near Microsoft-owned Github.
To be fair, this was not so obvious a choice in 2015 as it is now.
Github has (or used to have?) a feature to import SVN repos into Github, and you could use a Github Git repo via SVN, which is probably why they mentioned Github specifically. Other git hosts didn’t have those features.