I've got an old wallet that I tried to open and transfer out of but it won't connect to servers.
With the previous patch in Electrum servers, the only server that'll let your connect are either those that aren't patched which is highly unlikely to exist
or the malicious ones that'll show you a message with link to a fake Electrum download after deliberately failing to broadcast a transaction.
Overall, you have no choice but to upgrade.
If there's a compatibility issue that you're avoiding in v4.x, you can choose v3.3.8 which is the highest v3.x that you can get.