I swirched to fairphone almost exclusively because their phone has an easily swappable battery (it's very modular and easily repairable on top of that)
But if I'm not mistaken then there are new EU regulations coming that demand all batteries be replaceable, so hopefully this won't be an issue for much longer
The first thing I did with my Fairphone was to root it, and tweak the internal BMS/charge controller settings via a terminal. My ~4 year old device battery pretty much still runs like new, still get 2 days of standby.
From what I read on the FP forums though, users running stock tend to swap out their batteries every 1-2 years, like I had to on my old Galaxy S5. Most manufacturers' default battery charge profiles target the longest runtime, causing batteries to really degrade quickly.
For consumers that upgrade every 1-2y they won't notice this issue, but for those of us who want their phone to last longer than that, we notice this really quickly... in these cases having a swappable battery is a must
On the topic of modularity, I had my FP's vibration motor die on me, that was a very easy fix of literally opening up the device, swapping the module, and done. Absolutely love it!
On my device the charge is set to cut off at 91%, with the maximum charge current set to 500mA. If I'm in a hurry though I typically boost the max current to 1.1A, or the manufacturer's 2.7A if absolutely necessary (although I think that's a bit high personally).
To be honest a 1A max charge current would be a good balance between charge time and battery longevity IMO - the main purpose of the lower charge current is to reduce internal battery heat during charging, change the growth characteristics of lithium dendrite clumping within the battery, and reduce the chance of the battery swelling.
I also try to not discharge below 30%.
I'm not an expert on any of this at all though, I just mainly follow Battery University and some takeaways from a handful of research papers analyzing Lithium-based batteries
They don't have to. Nobody designs their apps to work with specific ROMs, they design it to work with Android. Custom ROMs are still android ROMs, they're just managed by open source communities instead of phone OEMs.
But if you have the 'wrong' version of android, the app will simply refuse to work. These kinds of apps are understandably picky because of security. And you can't expect banks/governments to make exceptions for a small minority who uses a custom version of android.
That does not depend on the version, but on google's safetynet. Apps can check with it if your phone runs an approved installation, which means not just being limited to the original ROM, but one that still contains all the garbage data mining apps that will also drain your battery and your mobile data plan, besides taking away your privacy.
Who do you think that custom ROMs don't use the latest version of Android?
And what do you think "custom version of Android" means? Every single android phone OEM needs to make their own ROMs. Are they all running custom android? Even Google pixels?