I have had no issues downloading apps I need that are in the normal Play Store. It seems to have the same functionality that I had with my Shield. The same apps that aren't there have to be side-loaded, just like on my Shield when I had it here ( it is remote as the DVR Server in PA now), as I recall.
I just side-loaded Google Chrome here and then it all worked:
https://apkpure.com/google-chrome-fast-secure/com.android.chrome/variant/81.0.4044.138-APK
Looks like someone figured out how to switch to SDR: https://www.tivocommunity.com/community/index.php?threads/access-tivo-stream-4k-hidden-a-v-menus.577379/
Just to follow up on this post for clarity, I saved the apk to my PC, then uploaded it to my Google Drive and then used X-Plore app on the TS4K to load it. I also used this process for sideloading the Xfinity and TiVo apps.
Let's hope they don't have to add a clock to the interface.
I'm all in on the Shield TV, but I hope Tivo sticks with the Stream 4k for those who want a cheaper device. I'm not convinced they will though based on their track record.