Being outside on my own is pretty good in general. Walking or cycling are the defaults, but maybe count as exercise? I've recently started riding a motorbike and spin on some quiet-ish open roads can be pretty rewarding...
Or do cardio exercises by watching various YouTube channels? (This is how my friend keeps fit.)
Other than that, there are plenty of inside options for that, like yoga (plenty of yoga series on YouTube), body weight fitness (pushups and whatnot, no equipment needed, though rings and/or pull-up bar are very handy), or aerobics (I count Just Dance games in that category), depending on what you're in to.
And of course afterwards you can light a candle and relax with a hot chocolate or some tea in the warm.
Why choose to live in a place like this if you don't enjoy it?