Right, I didn't consider SELinux, thanks for mentioning it.
TheEntity
Syncterm seems to be available in nixpkgs. It's trivial to install Nix (the package manager, not NixOS the system) on top of any system you choose and then add one or two packages you need, in this case just Syncterm.
"Local" in this context means local to this whole machine. From the perspective of a single user, it's system-wide. But then from the perspective of a sysadmin managing dozens of such systems, it's local.
If they are internal and permanent (read: unlikely to be removed on a daily basis), I'd just mount them based on their purpose and not them being separate HDDs physically. If they are meant for logs, mount them at /var/log. If they are meant for your movies, /home/user/data is more than fine. In general FHS describes the directory hierarchy, not which parts of it are mountpoints and which are physically on the same media. Technically you're fine having each and every directory on a separate HDD.
Honestly I can't say that I miss installing rootkits with terrifying privileges just to play games. I'd rather limit the privileges games have with Flatpak etc., not give them even more.
From their FAQ:
Q: What shells does Wave Terminal support?
A: We currently only support bash. […]
Seems at least dishonest to advertise it as a "terminal" if it works only with a specific shell. It's okay to have extra features enabled by escape codes emitted by the shell, but if it goes beyond that, I'd say it's not just a terminal anymore.
Obtaining it legally is one thing. Using it according to the license is at least just as important. Specifically if they trained it on content under GNU GPL or Creative Commons SA licenses, I'd like the result published under these licenses too.
Even back in the day when I still used Windows (and GUI almost exclusively) I browsed my filesystems like I'd use a terminal with tab-completion. I'd press the first few letters of the file/directory I was looking for and press enter, rinse and repeat. I knew my file organization by heart anyway. It's only natural for me to drop the GUIs for such use cases.