Both network providers are shown on the top left of the lock screen. However if the FP2 is unlocked they disappear. I am not sure if this was intentional or I am overlooking a setting?
FP2
Lineageos 14.1-20171004-Unofficial-FP2
Baseband 4437.1-FP2-0-07
Provider: Switzerland, Swisscom and Sunrise
Some telephone service providers apply modifications to the OSes of their phones and put them also in the always-shown notification bar as a type of advertising (quite annoying, in my opinion).
In vanilla Android, FP Open OS and community derivatives like Lineage OS, you can still check SIM’s operators unfolding the notification bar two times (a single one if you have no notifications). It shows the quick tiles panel, and each SIM should have its own tile for network data management, with the operator’s name within the tile.
But there is only one SIM card shown in this pull-down menu on Fairphone OS (usually the one which is set for data). I don’t know if there are one or two SIM symbols on Lineage OS.
It is the same with LineageOS. In the statusbar are two symbols in white (no config colors) and in the pull down menu is only one symbol for the mobile data provider.