Is there a cycling app equivalent of the couch to 5K please ?
...or just some advise on how to get started ? Beginners groups in my area ?
thanks, Tony

What bike do you have?

a Lot of local shops have group rides they do weekly (or several times per week) and of those, many have different rides for different skill levels. You Might want to check out some of your local bike shops to see if any of them offer this. Usually it's free to go along and the different group levels typically go from a fast, long distance "A" group to a slow, short-distance and more leisurely ride "E" group. That's how I got started.. I rode on my own a few times and then joined the D group and shortly after moved up to the C group where I mainly ride.. sometimes I join the "B" group. But it's a good way to not only test out and raise your skills, but also check out group rides and make some friends at the Local bike shops.

It's not like couch to 5k, but you'll enjoy Strava.

Depends on your area, depends on how you want to ride.

I'd go to Mapquest or RidewithGPS (my favorite) and plot a route in your neighborhood that won't include much traffic and if possible, only right turns at major intersections. Map a two-k route and ride it twice if you feel good ... three times if you can. Do this every other day for a couple weeks, adding miles if you feel like it.

I'd imagine even a "beginners" group ride would expect that you could use all your controls (braking, shifting, turning) and complete the ride in good shape. And I imagine you would want to be comfortable on a bike before you would want to have to watch out for all those other riders all around.

There are plenty of things like that. Many local bike shops lead beginner riders, as do some clubs.
For example, the local club in my area puts on a (100mi/50mi) ride for women. Starting about 5mo before the ride, they do a series of weekly training rides to help people train for the event.

Performance Bike has a regular Saturday morning, with a beginner appropriate option.