Look fab labs, hacker space, maker spaces or whatever it is named in your area. Those are not exactly everywhere, but common enough to have a look at. Another somewhat related space would be a repair cafe. That would give you not only access to a workshop, but also a bunch of folks for inspiration.

Other then that look up Arduino and RaspberryPi solar projects. It is pretty easy to find some lists. 3d printers are pretty common, as are many other similar tools. Home automation can also be interesting, but that might not be that great of an option, if you rent. Micromobility can also be somewhat interesting(elector skateboards, self assembling a bicycle…). It is also rather easy to set up a solar system in a flat, as long as you can easily install it outside it on a balcony or whatever. There is also a pretty large diy loudpspeaker community, which apparently is pretty easy to built.

Honestly there are lots of projects. Just think of something you would like to have and look up diy version of it. Seriously people built nearly everything at home. There even was a supersonic kit plane sold once, which apparently never managed to go supersonic and had a habit of killing its pilots, but you get my point.

You can check on arduino and ESP32 Boards for IoT. That was a hobby of mine, it never took off (albeit, a hobby so it’s fine). But I learned a lot about “low level programming” that had no idea it even existed, and there was some interest overlap with self-hosting (home assistant wasn’t around at the time, played with Mozilla’s mqtt). The latter did took off (I still enjoy doing it).

Anything metal or wood will probably create too much dust etc.

Maybe get a 3D printer?

I’m planning to build a solar powered weather station soon - I feel like that’s a project I could have done in my old apartment and put out on the balcony.

I’m just getting into bookbinding. It requires surprisingly few tools and not a ton of space (though like all hobbies it can always grow to consume whatever space is available). Its a good option if you have access to a printer with free or cheap prints.

Balcony gardening can be satisfying but might not be what you’re looking for.

If you already have a project (or lots of them) in mind, a 3d printer can be great to have around. Depending on your fillaments of choice (determined by what you want the print to be able to do) you might need good ventilation or an enclosure. If you have a spare bedroom that’s a good start.

this dude claims he made a cargo bike on his kitchen table. https://invidious.reallyaweso.me/watch?v=SDlnDEXlfm8&t=56