I think this is a fair topic.
I've very lucky - I live alone and self-isolated for 7 days which is now up. If I had a flatmate, it would have been 14 and we'd have been isolated together. I think there are two people in this world with whom that would not have been absolute hell and they are my dad and my sister. As such, all I had to do was find things to absorb my interest; plenty of new music from Bandcamp, a little bit of reading but less than I might have hoped, a film or two, some podcasts...hell, I even did a synch watch of an old Eurovision...I never had to consider how anyone else would feel about anything I was doing to keep myself going. Someone else being around immediately makes you consider that person too. I might want to listen to a 90 minute Miles Davis live album that is, in places, all-out percussive noise but very few others would find that in any way entertaining.
I think, for all the jokes people are making - and it's how we cope - it's an absolute bastard to be incarcerated with anyone.