If you do not use a local payment app, a city bus can still be practical. Beijing is a useful example because its official transport pages explicitly list cash and a physical transit card. Confirm the rules for your city and the route you intend to ride.
In Beijing, check the fare before boarding
The Beijing municipal bus guide lists cash, the Public Transit Card and a QR code as ways to pay. It says fares on suburban buses may depend on distance and advises passengers to tell ticket sellers their destination where that procedure applies. Read the route board at the stop, and ask the driver or ticket seller about the correct fare when you are unsure. Do not assume every bus has a flat fare or the same boarding arrangement.
Carry an app-free way to pay
The city's new-arrival transport guide specifically says cash can be used on Beijing buses and warns that drivers do not provide change. Prepare small RMB notes or coins before the bus arrives. The same guide describes the BEIJING PASS, while the bus guide identifies the Public Transit Card. Ask at an official sales or service point which physical card works for your route, where to obtain it and whether it needs a balance before boarding. A physical card can be useful for repeated trips, but availability at a particular stop is not promised by those pages.
If payment or the route is unclear
Show the destination in writing and ask which fare applies before paying. If you lack exact cash and have no usable card, find an official purchase or top-up point, or choose a different journey; do not rely on the driver having change. On a route with a ticket seller, follow that person's instructions for paying and keeping the ticket. Check the stop and service information again if travelling late or beyond the central city.
These are Beijing examples. For another city, use its bus authority or operator for the accepted cash, card and ticketing methods. A national travel guide cannot confirm a particular local route's fare or payment equipment.