Edited, posted almost at the same time,..as quixote ,
Any way, yes the wiki has some information,
I am surprised, if you have been doing research for several hours, I am surprised
you did not find this: (well maybe you did, but did not tell us) any way, https://wiki.debian.org/InstallingDebianOn/Thinkpad/Trackpoint
I found it using the same words the OP uses in the question.Trackpoint on the Lenovo T450 Thinkpad can be easily configured for Debian
It looks to me like it may not be very easy, and there may be some problems.
I wouldn't buy any computer if I can not check it first and make sure it really works, and as suggested a live CD would be a good way to test it,..
I also live in a very rural area, remote,... but when it comes to buying a computer, I go to the city , and store. No way would I buy one with out being able to test it.
How ever, a thought, Why don't you contact the manufacture of this hardware, they should be able to tell you, if not I would look for a better brand, even if it
did cost more. Of course, I don't know if you can take a salesman word for anything, they probably will say "Oh sure, man, we tested it on everything no problem, it works just fine",...