I don't have any child, so I might not be on point, but I am a lazy person by nature. When I was a child I was doing homework for ages, when it could have been handled in a matter of a few minutes, just because I'm really good at distracting myself.
Something that came to my mind when reading this question is the lack of positive reinforcement for your child. Something I might try is to promise him to reward him with sweets or an episode of his favourite show, if he finishes the assigment.
Another thing that came to my mind is, that you might compromise with your son, by telling him that you understand his situation (let's be fair: writing can be annoying at times, especially when you're not too comfortable with it yet) and that you'll both "trick" the teacher by just writing for maybe 20-25 minutes. That way you might ease him to do the task, since 20 minutes is way less time compared to the full 30 minutes and if he writes properly for 20 minutes, thats way better than discussing and procastinating for 30 minutes. Just make sure that he actually works for that time, since otherwise that "deal" wouldn't work, and you'd have to go back to 30 minutes.
However those were the solutions that came to my mind. Maybe try asking the parents of other classes, how they deal with their child's homework, while corona. You might get some useful input there as well.
