Almost all tracking is "third-party" unless it shares the same domain as the pages the visitor is on -- and this is only of relevance to cookies. Technically, if we or another tracker are storing your data on servers we control, its not really "first-party". But, this doesn't matter so much.
On the cookie-side, with FunnelFlux you can use unlimited tracking domains, so you can set up your tracking on go.lander.com and minimise this issue -- by using a subdomain of your landers. However, we try not to rely on cookies in the first place.
Note if conversions happen on some domain/page you don't control, such as an offer from an affiliate network, there is nothing you will be able to do about our JS tracking being third-party here from the browser's perspective.
This has little to do with iOS 14, the more worrying part are browsers and extensions generically blocking third-party JS/cookies -- but having simple JS blocked is rare.
We try to avoid relying on cookies at all, and would recommend using our server-side tracking when possible since this cannot be blocked by browsers.
Note if you own the pages and entire flow, you won't need to worry about blocking of your tracking as you can keep it first-party and carefully pass data between pages to minimise issues.