What even are they and should you use one? I’ll try to explain what they are even for non-techies and then give you my opinion. Sounds fair? Let’s go!
If you buy a phone it comes preinstalled with an operating system, that being Android most of the time or, if you buy Apple, it’s one of their IOS or tabletOS systems. A custom ROM is a different operating system that you install to replace the one that came with your device.
There are many reasons to install a custom OS on your phone ranging from privacy enhancements to “I just like it better” - different ROMs different usecases and reasons.
I have been using GrapheneOS for a year now and for the most part all is fine, you can get Mails, phone-calls, Signal works and all the usual stuff works… well not quite.
Most google services just die because they need the google-play services which are not installed and many apps depend on google SDKs that assume that it is installed and just die on boot or don’t start at all. The fact that for example online banking doesn’t work has been my deal-breaker. I am currently having to manage two devices the “smartphone” phone and the “banking and maps” phone (Because maps doesn’t work that well). This has never been practical and is unnecessarily complicated, i’ve realized that now.
Maybe i’m just lazy or dumb and can’t get it to work and I’ll get an angry mail explaining how to do this but frankly i’m now tired of this, I’ve poured hours into stuff other people never even think about because “It just works”.
Based on my subjective weighting of the points above and on my longer-term usage of one of the available systems my conclusion is that the hassle is not worth it (for me). Maybe your experience is different and none of the downsides exist on your ROM, in that case: Throw me a mail, maybe i’ll give it a second chance.