Virtual riding is an interesting one - is riding 200km on a turbo ever likely to be considered an audax?
No
And neither me doing 200km around our local 5km circuit which is a pity as I fancied that; only 40 laps!
I have done a fair few virtual events without going anywhere for charity. For example Coast to Coast on a stationary bike and big map behind logging distance with markers being moved along to show position and big buckets for the cash. Easy £1400 in a relatively short day.
I was considering Sainsbury's to the Somme this year in aid of RBL. I normally spend the Poppy Collection weeks in a local Sainsbury's collecting, but as it is the 100th commemoration of WW1 my mind thought about something different and so the stationary bike idea in the entrance and riding to the Somme.
Also done things like relay team to swim the channel in a swimming pool and climbing Everest via stairs.
Someone I know who was a very TT in his day did virtually all his training on a turbo as he had consistency; did exactly the same in the winter as in the summer. Worked very well for him as he was time poor and could not get out during the day other than when he raced.