Well, I follow Bitcoin only since early 2017 but fundamentals (in equity you use quantitative and qualitative metrics) which are (directly or indirectly impacting Bitcoin) in my opinion:
Thanks to Jameson Lopp and Willy Woo 2018 commits & contributors : Bitcoin 3274 , LND 3050
Bitcoin Lightning evolution + Blockstream Satellite launch
Google scholar articles mentioning bitcoin in 2018 : 14,400 (from 136 in 2010, 4'680 2015)
Segwit adoption near 50%:
https://transactionfee.info/charts/payments/segwit ( full SegWit adoption will bring blocks up to 2-4 mb range ?)
Mining difficulty strongly trending upward + GEForce GTX 1080 out of stock
Blockchain industry Venture capital funding in 2018: 3B USD from 0.8B in 2017 and 0.3B in 2014
Growth rate of Bitcoin reddit subscribers +61% in 2018.
FIO Protocol evolution :
https://fio.foundation/ for a killer app, user friendly/mass adoption?
Guys like Spencer Bogart, Pantera Capital, Mike Novogratz, Tom Lee, Anthony Pompliano, Tim Draper putting huge ressources on it. (Yes they are speculators I know, but speculators also help providing blood to the bitcoin's heart. Tony Robbins also talking about it
Crypo ATM market doubled in 2018.
Can book 550K hotels in 210 countries in the world using Bitcoin :
https://Travala.comGuys like Andreas Antonopoulos, Erik Voorhees, Max Keiser supporting and educating us about Bitcoin on a daily basis.
Maybe the price overshooted fundamentals in december 2017 but they seem improving not deteriorating. Sure for now sentiment is a strong "fundamental".
Well I could write a book with all the Bitcoin direct on indirect fundamentals, ho thanks to the The Bitcoin Standard: The Decentralized Alternative to Central Banking by Saifedean Ammou.
Hope they are getting stronger. "Every year Bitcoin survives, it demonstrates the resilience and robustness of the protocol, market, and industry that supports it."