That depends on the device. Some devices have native support for H.265, some don’t.
If this tablet is an old model, it might not have support for H.265 yet.
New Android device. The tablet is a Samsung Galaxy Tab A and it wont play it. Even if I try my Samsung Galaxy A71 phone it wont play it. No issues on Roku or Apple TV, but doesn’t seem to like the Samsung products
Google says that the Samsung Galaxy Tab A was released first in the year 2018. So even if you bought it now, it is on the technical level of 4 years ago.
It is apparently also very restricted in terms of RAM. There are only versions with 2GB and 3GB RAM available.
This might be an issue. (I know that the small version of the nVidia Shield also has issues with only 2 GB RAM).
You don’t do that on the tablet. You use the web app and access your server, using your server admin credentials.