Is there a way to automatically ask my 2017 to stop charging at 80%?

It appears that charging to 100% is bad for my battery and also normally unnecessary. Is there any way to set the charge timer so that it switches off when it reaches 80% instead of 100%? Is that something I could do with leafspy perhaps? Or does the car automatically do something behind the scenes that helps I'll set the battery life issues with returning to 100%?

I wish but nope. Best you can do from the car is set a charge timer and you calculate roughly how long to hit 80%. Another way is my EVSE at home lets me set a power limit (or time limit if I wish) so I can calculate how much power is 80% and have the EVSE stop providing the charge at that point. Some other brands like Tesla do have such charge limit settings. One thought as to why Nissan removed it is they may be rated differently in the range?

No. The 80% limiter was removed on US models starting w/model year '14.

Best you can do is limit it via timers, unplugging early or getting an EVSE (e.g. Juicebox) that can reasonably guesstimate when to stop. You need to tell it what car you have the 1st time and each time afterward, you'll need to enter your current SoC to have it properly stop at the desired SoC.

The below and being hit by a stupid 80/100 averaging "rule" seems to be why Nissan removed it. In model year '14, 75 miles didn't look so good vs. other sub-100 mile EVs while 84 was near the top.
https://insideevs.com/news/317213/2013-nissan-leaf-rated-at-75-miles-but-84-miles-using-the-outgoing-2012-epa-ratings-system/
https://insideevs.com/news/320736/2014-nissan-leaf-mostly-unchanged-as-range-technically-moves-up-to-84-miles/

Yes, Dala (who frequents these forums) has a BatterySaver feature that he has coded for the MUXSAN CAN bridge. However, purchasing a CAN bridge for this feature only likely isn't worth the cost to you.

In case you want more info, see the "BatterySaver" heading on this website:

https://dalasevrepair.fi/#products