(Assist) English no longer available after 2026.6.3 update

Hi!
I've been having a weird issue and I would love your input on resolving it. I hope it's simply me being a dummy, but I've done some basic testing and I'm perplexed on what's causing it other than a bug.

Problem : after upgrading to 2026.6.3 from 2026.5.4, the english language is no longer available in Assist as the configuration language. This affects new and existing profiles, all other languages are working (my French profile works), but English is no longer available and usable by my assistant.

Debug steps:

  1. After finding the issue, I reverted to the backup just prior to the upgrade from 2026.6.3 to 2026.5.4. The problem remains, which is surprising.
  2. I've cleared the cache and local files from my browser. I've also forced refresh the webui, the problem remains.
  3. I've tried on a different computer and a different browser (tried on Firefox, Brave and Edge). I've also tried from the Android app. The problem remains.
  4. I've removed custom sentences just to check if this is the issue. The problem remains.
  5. I've booted in safe mode, the problem remains.
  6. Looking at the logs, I don't see one that could explain the issue.

Do you have ideas of what could cause this and what debug steps I could do to identify where the issue is coming form?

Thanks for your help!