It is only for Web
Is it me doing something wrong? (Which i doubt)
Cuz in early versions of Unity6 it was all good as well as in current LTS but for the latest versions of Unity6 subscenes don’t compile at all. (Not present archive content folder (or something like that, forgot a folder name already) in build)
Tested on an empty project with only one entity in subscene.
I can understand a bug only in one version but in a three in a row? Or it is just me problem?
You are aware that Entities is not (really) supported on the Web?
Even if it has been working (I’m surprised but you may have been lucky simply because you haven’t been using something technically incompatible yet) there is little to no benefit in using Entities on the Web since you get neither multithreading nor Burst optimizations.
yes i am aware that it is not support Graphics package as well as burst. But my project is multiplatform and you can use Entities package in web (i mean Mono also dont support burst and multithreading so what 
)
It is just recent unity versions for some reason broken for me.
Well, it seems this problem exist at least since 6000.0.10+ (i tired to check every version)
What happened with DOTS for web? Is it not supported anymore?
Will it be fixed?
My assumption is that DOTS simply has no priority for the Web UNTIL we get to have C# multithreading respectively with the next tech cycle with deep Entities integration (each GameObject will be an Entity behind the scenes).
I mean whats wrong with web? Especially if your game is multiplatform.
I am not asking for all benifits of DOTS in the web platform but only loadable subscenes on a main thread. Like it always has been but in recent versions they broke it and dont fix for some reason.
This post sheds some light on the development. A few posts earlier there was also mention of a subscene load issue. I get the impression these kind of issues will appear again and again for as long as DOTS on Web is not a priority.
I’m facing a similar technical issue where the “host-alone” singleplayer approach will not work on the Web, since you cannot host with WebSockets. Even though technically it would be possible to just use the fast-path of direct method calls for RPC calls. Instead, I have to write extra methods that either make a direct call or call an RPC depending on whether the player is “offline”.
Well it seems the whole Unity6 dont support it.
The last working version is Unity 2023.2.20f1