I can confirm still not working on 20270 have reverted back to 20251 and games work great. I'm hopeful that Microsoft will address this issue have been on feedback hub as well and have had no response from Microsoft. I don't want to but I am seriously considering quitting the dev channel, I'm started to get annoyed now, I want to update but cannot, it seems like we are being ignored due to the fact this is 3rd party I.E Ubisoft and not an MS or Xbox related issue with there apps or software.
Per Eddie:
We're investigating this one. Would you mind filing feedback and share the link with me?
-Eddie
Not everything gets fixed in 2 or 3 builds.