Want to avoid last-minute ATM runs. Do most hostels in Lebanon take card payments at check-in
I'd be very cautious about relying on card payments.you can even bring a good amount of US dollars and use that for your hostel payments and other daily expenses.
You'll need cash for sure. I stayed at a few hostels and small hotels in Lebanon, and not a single one accepted a card. They all required payment in cash, preferably in US dollars. The local currency, the Lebanese lira, fluctuates wildly, so many businesses prefer foreign currency. Don't rely on being able to use a card to get cash from an ATM, as that is not a reliable option.
Don't even bother with cards. I was just in Beirut last month and tried to pay with my card at my hostel, and it was a complete no-go. The place wasn't set up for it. My advice is to assume that you will not be able to use your card for hotel. You'll need to go to a money exchanger to get US dollars to pay for your stay.
You're going to want to carry a lot of cash. The financial crisis in Lebanon means that even if a hostel has a card machine, they might not be able to process international payments. Most of the smaller, independent hostels in Beirut like Hostel Beirut or The Colony Beirut Hostel are strictly cash-only. They prefer to be paid in US dollars, so make sure you bring a good amount with you.