How big was the house?
Small two bedrooms
Did your mother sit and work in effectively the same room, while visible to the children but ignoring them?
No, she was in the living room we were in the bedroom.
Was your mother on Teams calls which required no noise, yet sitting in the same room as you all?
No, she had groups of people in with her, did require no noise. We were in the bedroom.
What methods did the nanny use to ensure no interruptions and would they be comparable with the values and behaviours of most loving parents now?
We played. Yes, nanny was lovely and kind.
I can’t help wondering if the answers to the above questions would show that your experience isn’t as relevant to this situation as you imagine.
No, they don't. That's why I talked about my mother. Dh also worked from home while dc were tiny but the house was big and it was mostly email (yes, and calls which required silence), so it was much easier for me when the dc were small.
Fact is, if OP wanted to she could do it but she resents it so isn't willing to. It's her right to refuse to help her dh to work from home if he has an alternative, but it's disingenuous to suggest that what he's asking is impossible.