$ sudo touch /etc/ssl/certs/foo
[sudo] Passwort für ogra:
$ snap run --shell telegram-desktop
To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details.
$ ls /etc/ssl/certs/|grep foo
foo
$ exit
$
Your snap should definitely see the added certs … (it surely does here)