Apart from the HTML5 export mentioned by another commenter, there exists Ruffle[1], a Rust + WASM reimplementation of Flash that can play swf files. It's used a lot on archive.org or on some websites like https://homestarrunner.com.

[1] https://ruffle.rs/

It says:

> HTML5/Canvas export — Export to self-contained HTML5 with JavaScript Canvas 2D playback.

Call me crazy, but I think the folks at newgrounds will figure out what to do with this new flash.