When I update to 6.0.1 it hides categories, Featured image, Author selection when I want to create a post

[digital2019]

Since I updated to v6.0, when I create/edit posts, the Author, Category and Feature Image tabs on the right-hand side have disappeared.
I’ve tried disabling plugins and reactivating plugins to determine if it’s a plugin compatibility issue, but I don’t understand why it would be. But nothing worked.

My user account is a full admin.

After searching, I can see that some people have had the same or similar issue, but their solutions (deactivating plugins etc.) didn’t work for me.

[makmal]

Same issue here, but with Featured image.
Tried everything, everything. Disable plugins, cache, cloudflare, restore backup, different computers, browsers, replace theme. It's not even in the panel list.
In my mobile i can sometimes see the panel, some of my finds can see it but no categories. In other website i have everything is fine.
Plugins such as WP-Rocket, Yoast, wp-reviews that lastly update has been disabled.
WP_debug showing some errors related to the themes but i doubt it related.

[alanjacobmathew]

From the image attached I can clearly see all those sections you've mention missing.
Test it with TT2, and no plugins installed.