The rail line on that section is FEVE and is the "commuter" line for the north. Commuter is a bit of an odd term as the rail line runs through the countryside there with lots of great views of the coast. I was on it just this month
The train is like an urban light rail and on some sections, its on-demand as you have to indicate to the driver if you want to get off or on. Also depending on the distance travelled, you might have to switch trains as the trains relay. You get to a station and everyone, including the driver, gets off and switches over the platform. The arriving train does the same. It's very off-putting if you don't know where the switch happens but the drivers/guards (if present) look after you.
You also pay on the train (cash) or at one of the machines (card) in the stations. In the smaller stations staff, if there are any, work for ADIF and not FEVE or Renfe. A lot of the stations have nothing other than a shelter and can be a distance from a village. Locations are determined by the rolling landscape and gradients. There are no trains after Ribadeo where the Norte turns south.
As regards timetables, you can get them on the Renfe website under the Cercanias/Commuter headings. What was far more useful was the ADIF app on my phone which told me which was the local station, it's location and the arrivals/departures in real time. Renfe app is not much good in FEVE countryside.
www.renfe.com
www.renfe.com
I'll leave others to advise on buses but I saw plenty of
Monbus vehicles on the route. Some pics from the train.