If you’re getting free weights, I’d get an adjustable bench as well. If you already have a bike, you can get a bike trainer to ride inside when weather isn’t cooperating. I’d avoid a treadmill since as you mentioned, the outside is accessible, and if you’re not in a climate with snow and ice, a little rain sometimes feels good during a run.

But like others mentioned, dumbbells and a kettlebell will be all you need to do a lot of strength exercises. An adjustable bench allows you to expand on that. You can get dumbbells that use plates, so you dont need a full set, just the bars and plates. In the future you could get other bars for different strength training if you feel the need and you can just use existing plates.

Otherwise as someone else mentioned, you can do a lot with just bodyweight traing too. A good mat will go a long ways for that. You can supplement that with resistance bands that take up minimal space.