Ask for their email, then pen and paper. Or keyboard and a local, maybe synchronized contacts list.
No, not sarcasm, no, not joking. I had decades old email addresses of friends I pinged when the lockdown started, and the vast majority of them got to the intended person.
EDIT: yes, one by one. If they matter to you, they should worth the time.
What's sad / frustrating / predictable is that they had an open API until early 2016 to export contacts. No mistake they shut that down to lock folks to the platform I'm sure...
No, not sarcasm, no, not joking. I had decades old email addresses of friends I pinged when the lockdown started, and the vast majority of them got to the intended person.
EDIT: yes, one by one. If they matter to you, they should worth the time.