What I have found 4 me as a partial answer to how to bike during the Covid times

[BikePacker]

I have found that with so many peeps staying home that (sadly) there are many, many vast vacant parking lots all around my vicinity.
These make, for me, a great abundance of large open fairly level places to safely put a free & open spin on the spokes,
along with enough time in saddle to keep in shape till 'the bug' passes enough to make Touring practical again.

[Pat Lamb]

Streets and roads are even better than usual with motorized traffic way down.  I did a loop just before supper tonight, right during "rush hour," that I'd never ride by choice in normal times.  Fantastic!

[Mark Manley]

It's a similar thing this side of the pond, lots of lovely empty roads and great weather, although we are only supposed to go out for an hour I still make the most of it. 

[canalligators]

Around these parts, we've seen a significant increase in users on multi-use paths.  They're downright crowded at times.  Roads are better for staying away from other people's exhalant.  Fortunately for me, my county is laced with roads that are pleasant to ride on, have fairly light traffic and the drivers are mostly courteous.

I did see a family riding in a parking lot, but the kids were young so that's where they'd be anyway.

[froze]

I've been riding my bike outside without a face mask, as long as you are at least 15 feet away downwind from the next rider you'll be fine, but I seriously doubt someone with C19 will be riding their bikes!  I'm not that paranoid about this virus I pass jogger and cyclists and maybe have 4 feet between us.  Also where I live the cases have been low in number.

Yes I know the protocol was 6 feet but that is a stationary person to stationary person, the faster one is moving the further away you need to be.

Supposedly the newest theory is that the more fit a person is the least likely they will catch the virus, and if they do they won't get it very severely, more like a minor flu.  Note, I said theory.

But you all need to take whatever precautions you feel necessary to give you peace of mind, and if that means cycle indoors than do it.

[canalligators]

...
 but I seriously doubt someone with C19 will be riding their bikes! 
...

Not true.  You can be contagious while exhibiting no symptoms and feeling fine.  For all I know, I could be infected.  That's where the mask comes in; it helps prevent me from infecting someone else.

[BikeliciousBabe]

...
 but I seriously doubt someone with C19 will be riding their bikes! 
...

Not true.  You can be contagious while exhibiting no symptoms and feeling fine.  For all I know, I could be infected.

+1. I cannot believe people don't know this. While the true percentage of asymptomatic cases may never be know, here is one striking example. 96% of this inmate population tested were asymptomatic:

https://thehill.com/homenews/state-watch/494670-ninety-six-percent-of-inmates-in-four-state-prisons-who-tested-positive

[BikePacker]

here is one striking example.

Thank you Bike .... while I barely survived stats class I learned nuff to conclude that this article
(along with it's Reuter's source) are likely ok combined sampling.
If so, this is added value to the notion of 'herd immunity' as the final/ultimate Covid stopper.

[froze]

...
 but I seriously doubt someone with C19 will be riding their bikes! 
...

Not true.  You can be contagious while exhibiting no symptoms and feeling fine.  For all I know, I could be infected.  That's where the mask comes in; it helps prevent me from infecting someone else.

Your right, someone may have it an not know it.  However distance is the best guide, read this for more detail:  https://blogs.webmd.com/webmd-doctors/20200410/is-6-feet-enough-distance-when-walking-and-running

I'm not wearing a mask while riding because where I live it isn't a heavily dense biking area, and I go mostly on roads and not bike paths, so I rarely run into a cyclist.  On the bike path I may run into a lot of riders, but they're not usually riding fast.  I'm just not worried about it.

If my immune system was bad then I would be a bit more worried about.

[hikerjer]

Froze's outlook is much like mine. While I always wear a mask in crowded public places, but when I'm riding I don't. I don't pass that many other riders and pedestrians and when I do, it's very quickly. i just do't think it's an issue in those particular circumstances.