Or should this be more specific in that you shouldn't shorten URLs using the provider's domain name, but bring your own domain. So if the provider goes away, you can in some way migrate the links.
That's why I set up my own thing. I don't care about analytics at all, so I just wrote a simple build system doto generate some very basic HTML redirects.
It isn't perfect but it's very cheap to run!
/ https://example.com
/cv https://example.net/cv.pdf
/git https://github.com/octocat
Even if the supplier disappears, it is possible to quickly switch to another platform