The compressed Textures stopped working last update.
I have reverted back to v6.20.2 and they work using that version.
If I add console.log(formatUsed); to the playground above I see it does the detection correctly (giving me -dxt.ktx in Chrome) but does not render the texture nor give an error 
Sorry for the trouble, I introduced a regression in a PR 3 days ago.
Here’s the fix:
@sebavan , you may also find this one interesting re: compressed textures. Apparently lots of basis texture stuff is broken in other engines on the latest ios safari 17. Here’s the related webkit bug: 260252 – REGRESSION (Safari 17): WASM intermittent failure transcoding basis file (webkit.org)
and PS: this is how playcanvas got around it, in case relevant: Important: Basis on Safari 17.0 - Announcements - PlayCanvas Discussion
@bghgary and @Evgeni_Popov is it smthg we should do ?
I don’t know, I’m not sure a lot of people are using the basis layer in Babylon.js, they generally use compressed textures through glTF, which is using .ktx2 textures…
It seems like recompiling the WASM also fixed the problem, so we can just wait for that to happen and pick it up.
Let me assign the thread to you so we do not forget once it is ready 