Carbon steel! I have some de Buyer acier carbon steel frying pans which are great. I bought mine from knives and tools:
https://uk.knivesandtools.eu/en/ct/de-buyer-pans.htm .
If you go cast iron or carbon steel you need to research how to make them non-stick (known as "seasoning"). It's pretty easy and there's lots of info on YouTube. Basically you want them to look completely black rather than the shiny silver like they come. In a very very short nutshell it's basically just a case of coating them in oil and sticking them in the oven for an hour or two. I just used normal olive oil rather than flax seed, but anyway:
* I actually bought from their EU store because it was a few quid cheaper for each pan than the UK store and was free delivery, just use the translate option in Chrome. They came in a couple of days. Check their
French site,
German site or
Netherlands site - each have slightly different prices.