Look on ID Market. Chicken enclosures come ready made for fruit cages (frame and chicken wire) - the large ones substitute net for the roof. (I had an old roll of chicken wire I replaced it with - but that’s more fox/Martin protection). With delivery usually 100+ for a 6m2 - but depending on size they get more expensive. They discount heavily now and then - I last paid 200 euros for 20+M2 delivered on offer for the big chicken run. Bricoprive also has discounts quite often on idmarket products.
My guinea pigs have been in one for 6 years now - and the chickens two years. Frames are fine. Given what I know now - I’d have sprayed the frame black for the guinea pig one as it’s right outside the kitchen window/outdoor eating place which would make it a bit less “ugly”
The 60 euro L’clerc sales polytunnels have a limited life - but the slightly better ones survive years.
I’ve lashed together small frames/covers using the bits left after the storms wrapped the cheap tunnels around a tree (work fine but so not pretty).
Without the plastic cover they don’t get destroyed by storms or heavy snow - and the water doesn’t hold so the frames survive.
Avoid the 10-12mm diameter frames - the 60 euro tunnels. But the next price up are enough.
Chicken wire you can get tight and it’s more bird friendly - but obviously you can replace it with netting if your using a poly tunnel frame.