However they are not stating which wallets are affected. Only that so far $900,000 was stolen due to some poor random number generator when generating seeds.
How do we find out if Electrum uses this dependency?
The Libbitcoin library is not a dependency of Electrum. Even though Electrum and Libbitcoin both deal with Bitcoin and cryptocurrencies, they are independent endeavors with various goals. Electrum's main functionality is neither directly included into or dependent upon Libbitcoin as it has its own codebase.