Could you look at soundproofing against the neighbours noise?
Plant a kitchen windowsill herb garden, I know it's not a garden garden but you can search online for ideas to cultivate indoors might just bring a bit of joy.
Can you have a rethink about moving towards more cash career wise, that might just bring the possibility to move closer, no it won't happen this year but you might be in a position in 3 years.
Sometimes it's not about changing what you can't you have to change what you can.
Even in a flat you can still cook/bake great food, read amazing books (if you have join a local library and start ordering books that look your thing), listen to music, play music, have movie sessions.
Can you look to explore new local outdoor space? Parkrun might be a good starting point for your family. It's free and gets you out. You can walk it if need be it's only 5km which is just under 3 miles.
Even something as mundane as painting your front door a bright colour, or suggesting with other flat occupants a car park BBQ in the summer?