My kids and wife know there is a rule during work hours:
When my office door is closed, I am not home (except for emergency, say broken limb or something). It takes some training, but they become accustomed to it.
You need to stress to your partner the importance of focus during work. This took an exceptional amount of effort for us because my wife is bipolar and when things are bad, her contributions become a trickle. Summer is always a trying time, because all the kids are home and she gets overwhelmed easily. Thankfully my employer is incredibly accommodating, so if I need to step away and resolve anything at home, they have faith that I'll see to my obligations.
There's certainly value in having a dedicated work area if possible. Your brain really likes having demarcation lines between work and home, so emulating that can help immensely.
It is important to note that WFH is NOT a silver bullet. It is not a solution for every employer/employee. It works incredibly well in many technological scenarios because of remote access and whatnot, but there are limiting factors. Both in bureaucratic requirements, "culture" fits, and domestic situations. What works for me in the Great Plains due to cheap(er) housing may not work in metro areas where some families are living in small apartments.
Don't feel obligated to make WFH succeed in your situation if you don't want to simply because its en vogue. I have dear friends that tried WFH and _hated_ it. Another option is co-working space or otherwise getting out of the house to focus on work. I find myself going to a local hiking trail area during spring/autumn to work outdoors, and it is refreshing.