I am using LineageOS on my FP2 since a few days now, and so far without any problems. 
I formatted the SD-card as internal (adopted) storage and was surprised that the storage is then automatically encrypted. This is great and works well for me.
But there is also a downside and a warning for all who want to use the SD-card as internal storage: since the storage is encrypted, there is no easy way to access the data from the SD-card slot of your computer. You will need a Linux system and some experience with the Linux command line (more info about this e.g. here or here). You should also backup the key from /data/misc/vold since this is the only chance to get access to the data on SD-card if something breaks the system on your phone or you did a factory reset.