I'm aware that it is not easily possible with all game engines and it might not work for every game, but many Unity-, Godot- and Unreal-based submissions can probably be easily exported for Web.
My previous posts on the topic:
- Some explanation for web exports in Unity: https://ldjam.com/events/ludum-dare/47/legendary-orbit-golf/publish-for-web
- Guidance for the publishing process: https://ldjam.com/events/ludum-dare/38/where-is-mommy/submit-for-all-the-platforms
- Howto automate WebGL publishing with Unity: https://ldjam.com/events/ludum-dare/48/drillromantik/automating-your-unity-webgl-export-on-github