This app was mentioned in 19 comments, with an average of 1.63 upvotes
I use my icloud mail in samsung email app as it allows automatic sync when mail arrives which is missing in gmail app. Haven't tried any other email.
You can also try flux theme that's amazing too https://play.google.com/store/apps/details?id=flux.substratum.theme
The closest thing you can get to vanilla Android is to use a custom launcher (Nova is fine but for the proper stock experience you're gonna have to go with Rootless Pixel Launcher or Lean Launcher).
Download Substratum + Andromeda and find a theme that resembles stock Android, then apply that to the system. Flux White looks pretty good but I'm using Swift Black personally cause I'm all about that AMOLED screen. I'm also a fan of using Product Sans as the default font instead of that crap which Samsung phones come with.
If there's a Samsung app that has a Google equivalent, use the Google one instead and hide the Samsung ones from your home screen (this is for the vanilla experience, I'd recommend using S Health/S Pay/Samsung Internet over the Google alternatives simply because they're so much better).
Disable Bixby, or even better, assign it to Google Assistant using BxActions. You can even assign a single press/long press option, so feature wise it's better than the Pixel 2 squeeze.
That's about it in terms of what you can do to get the vanilla Android experience (outside of installing a custom ROM), and it doesn't require root in any way. Everything should be free except for Substratum + Andromeda + Flux White. Other people have mentioned how to deal with the battery, so you can read those instead.
I love it, pretty much a perfect rom for me, everything works. And yes there is a built in dark theme and if you don't like that you can always install substratum theme engine and install something like this
I had a number of crashes with Swift Dark, but I've recently switched over to the Flux theme. It seems to be more stable and includes some pleasing visual tweaks (like in the Quick Settings and Navigation Bar). The downside is that it doesn't have themes for as many apps as Swift (but you can always use both at the same time).
https://play.google.com/store/apps/details?id=flux.substratum.theme
To my knowledge there is nothing for Fulmics, and Lineage OS also does not work with Substratum, there is a solution but you will need to use another ROM other than Fulmics. crDroid is based off of Lineage OS, but crDroid does work with Substratum and has several dark themes that look great.
I know you wanted to find a solution in which you can keep using Fulmics, but it does not exist, I used Fulmics for ages and tried finding something that worked using Fulmics but I ended up flashing crDroid and have really enjoyed this ROM, especially because I can theme the crap out of my G3. My prefered theme is Flux it looks amazing.
You need to get on that Substratum tip and give Flux or SWiftBlack a try. Don't even need root for substratum once you get on 8.0
Swift themes are the most thorough i've found, but are basically custom background + stock accents. if you want something to really change the look, Flux has a really cool take on quick settings.
Here is the Play Store link:
https://play.google.com/store/apps/details?id=flux.substratum.theme
I feel like this theme came from Substratum (Samsung Overlay Engine). Link:
https://play.google.com/store/apps/details?id=flux.substratum.theme&hl=en_CA
I'd suggest a substratum theme FLUX (Or FLUX White) on Play Store. It costs a bit but it can get rid of the ugly orange. I tried an apk for the S9's messaging app I found on some site a while back but I ended up deleting it because it didn't work well and was missing features like scheduled messages and a simple search bar. Just a thought. Link below.
https://play.google.com/store/apps/details?id=flux.substratum.theme
https://play.google.com/store/apps/details?id=flux.white.substratum
Sure, it's the Flux Substratum theme. It's definitely the nicest that I've found so far!
https://play.google.com/store/apps/details?id=flux.substratum.theme