I feel your friend’s pain, truly. I’ve been working issues with my right foot for the past 5 years including 3 surgeries, ugh.
Does your friend happen to have a community rec center nearby? Unlike private gyms, rec centers don’t try to get you to sign up with contracts and are typically reasonably priced. Mine offers a daily pass, monthly pass, annual membership, household memberships, and “punch” cards. If you’re not a resident, they charge a little more because your taxes don’t contribute to the center, but it’s all still reasonable.
Go there and ask to just walk around and look at what the facility has to offer, they’ll let you do that for no cost. If they’re not busy, explain the situation and they’ll probably offer lots of ideas. The other thing I like about a rec center vs a local gym is I see all kinds at our rec center: young, old, folks obviously rehabbing from surgery, with walkers, with oxygen, etc.
Our rec center has a hand cycle, rowing machines, recumbent bikes, free weights, weight equipment (so no need for spotter), yoga classes including for those with physical limitations, all sorts of things. Our rec center also has pools. I know you said no swimming, but there are classes in water aerobics, which is great to provide resistance for muscles without the force of gravity. There are also a bunch of floatation belts, “barbells”, noodles, etc. to help with doing exercises if joining a class isn’t desirable. Our rec center also has a “lazy river” where I was able to walk against the current of the “river” but not pound my poor foot.
There’s also things you can do to “trick” your body into thinking it’s exercising, a sauna for instance, which the rec center may also have. A sauna gets a person sweating and raises the heart beat. Good as running a 5k? Probably not, but there IS benefit to this.
Here’s a crazy thought, near any lakes? How about kayaking? Okay you need a kayak to do this, but I remember one of the places I lived had a gym next to a lake and kayaking was one of the exercises they offered, I thought how fun!