Yeah, that looks pretty much like something has gone really wrong during the installation.
Why do you say that? Just normal Linux quirkiness I think.
Checksum was fine.
That's not "quirkiness". I have installed plenty of Debian installs in my life and this has never happened. Just to be clear - I am talking about getting a Thai terminal instead of US one by default, not having a Thai terminal in the menu in addition to a US one - which could be normal, either by choice of the distro developers for some reason or because it got pulled in as a dependency of something else that you have selected for installation.
By something going wrong I mean that installation of something could have failed and left the system in a partially installed state. I have seen that happen a few times - either because of a corrupted package (that's why the question about the ISO checksum), bad package on the mirror (if you have opted for installing/updating from the network) or sometimes simply a bug in the package. Checking the installation logs would tell you if that has been the case or not.
If you have installed Cinnamon, you should have got gnome-terminal installed. If it wasn't there, then that's not normal.
Xterm is the basic minimal terminal that needs to be there because of the X compatibility with older applications which expect to be able to find it. It is part of some kind of standard. Uxterm is the same as Xterm but it supports Unicode characters.
Here's another. File Manager in Debian XFCE Live was not able to open the local network.
Error message, Failed to open "/ on ".
I guess technically it still worked as a file manager. The problem turned out to be some missing gvfs packages. I decided to avoid Xfce for now.
That error message is stupid indeed but it is telling you it was not able to open a root directory of the folder you were trying to browse. The gvfs packages provide those virtual folders, e.g. for network or other things (e.g. a connected phone, camera, zip files, network drives, Dropbox ...) that are not really disks/directories but are to be presented as ones. So there is no "quirk" there - if you didn't install the required drivers for some reason, it could not work. That it would be better to not even offer browsing of the network if those plugins are not available is a different matter, but that you need to raise with the XFCE authors or Debian's XFCE packagers.
Debian's philosophy is minimalism by default - it won't install optional dependencies (such as those gvfs packages) unless you tell it to, because a lot of people don't need/want them. They may be tagged as recommended, though - but it is still up to you to tell the system to install them.
If you want distro that is a polished desktop experience without such "quirks", then Debian is likely not the best choice. It is a great system but for advanced users. They are shipping the various desktop environments and other software in their default configurations, as shipped by upstream developers, which sometimes means that the experience is not as polished as it could be unless you spend some time tying up the loose ends. Also given the sheer amount of software Debian ships it is probably not even possible.
If you don't want to be doing that, then one of the Ubuntus or their variants (Xubuntu if you like XFCE, Mint, Kubuntu ... ) will give you a lot less grief on the desktop. Or Mageia Linux if you don't mind switching to an RPM-based distro. These are much smaller in scope and the developers are specifically focusing on the desktop experience.