Since they don't make it anymore and that filters are extremely pricey, it's probably not a good solution here

a fume extractor can just be a length of dryer vent hose and a big PC fan. filter not needed if it goes out a window.

if you do use a filter make sure it captures metal vapor, which is unlikely with a regular hepa filter.

I use a different air purifier, a pretty basic xiaomi one. There are two downsides: it is quite big (I don't mind really) and it can be loud at a high speed.

I host movie nights with friends and sometimes someone might even smoke in the room, air purifier clears the air quite fast and there absolutely are no odors left. So yeah you can and if you solder or 3d print often, I'd suggest to get one, they don't cost much.

I'm not allergic and air here is basically always perfect - 1-5 ppm, but I still love it. It does filter out allergens and people allergic to pets find it easier to breathe (I have a dog). It also lowers amount of dust a bit, and I have an automation to run it on full speed when robot vacuums floors, I think it might help filter some stuff out.

I wish there'd be a way to put activated carbon packs inside somehow, because I'd love to change it more often than the full filter.

But then you still need to spend 70 pounds on a filter!

I suppose there are Corsi–Rosenthal box designs out there for 3d printing. We don't have filters like this here, otherwise I'd make such a diy purifier instead of buying one

yes, well for all new ones

but a bunch of years ago there was some blameless fan which worked somehow else (electric charges or similar???) and had the side effect of them emitting ozon

this is why if you google dyson+ozon you will find a lot of articles telling you in various details "no they don't produce ozone", because at least some dyson like fans did produce some amount of ozone in the past. Idk. if that also applied to some old dyson products.