More information:
I'm fairly certain that the Compaq RT101 and the Digital PCXAL-AA are mechanical, seeing as they were taken from an office, they were most likely never modified.
The DEC VT100 only works with the corresponding terminal, unless you want a hobby project to make it compatible with another serial bus. And because it's so specialized, only an enthusiast would probably want it.
The BTC I am 100% sure is rubber dome. The Logitech I'm 95% sure is rubber dome. These are more for those who really want the internet "surfing" buttons on the Logitech or the ACPI Power Management keys. Or for that 90's KidPix playing nostalgia.