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You don't say whether you have a garden, or access to one, which might influence your choice of breed. Thumbs up for rescuing/rehoming given the number of dogs that need it and RSPCA reports that the number of abadoned and unwanted dogs is already increasing due to Covid-19
I'm biased, but a Staffy would tick your boxes in terms of size, the amount of exercise, sharing the sofa, not docile - and there are loads that need a good home.
And having a dog has been good for mental health, particularly at some very dark times...
I'm not tied to a breed at all, but a large dog would be inappropriate for the size of the flat and my current weekend habit of driving out of the city and going for an 5-8 mile walk in the country is better suited to a medium dog that isn't excessively docile.