I haven't read through he first 200 posts here, so I'm sure this at least partly rehashing things.
Anyways, I don't really blame Gebbia for wanting to leave, but it's kinds of an odd decision. Why not wait until the end of the regualr season? There's no guarantee that Martinez stays healthy. He could also get benched for struggling. Nebraska has had at least one game that the backup QB played extensively, either because of injury or ineffectiveness, each year since 2013.
2013: Taylor Martinez, Tommy Armstrong and Ryker Fyfe each started at least once.
2014: Armstrong left both the Michigan State and Iowa games for a time.
2015: That Purdue game we all want to forget.
2016: Ryker started against Maryland and Tennessee and played a lot against OSU.
2017: Tanner Lee missed a bunch of the Minnesota game.
It seems short-sighted to me for Gebbia to leave right now when he could leave in December. Heck he might end up starting here for six games and become the full-time starter. Worst-case scenario, he transfers in December as a redshirt freshman and after sitting out can play two full years at his new school.