I can install the latest LaTeX in my Debian 8.5 as described here at the end of the question body. Apt-get does not have the latest Lyx (2.1.2 < 2.2.1), but I would like to have it and control it centrally with my LaTeX installation. I could not find anything about it with the tool install-tl.
OS: Debian 8.5
i dont think the install-tl tool can control the update of LyX. Lyx are independent of TeXLive (i suppose you use TeXLive).
But look at this link : https://www.guyrutenberg.com/debian/jessie/ You can find LyX v.2.2.1 for Debian Jessie.
I have not test it because i run on a FreeBSD box.
I hope this will help you!
