I have recently purchased a new phone (Laude M8), which is the first Android 5.1 phone I have used, and also the first phone I have used which supports dual SIM cards.
I have only one SIM card inserted, which is from a Lithuanian carrier. When I restart my phone, it boots with the Lithuanian language selected and I have to manually change it back to English every time in Settings -> Language & Input. Disabling the SIM card in the options makes no difference to this behavior, but physically removing the SIM card works to stop it changing the language.
Is there a way to force it to always boot into the English language with this SIM card inserted?
My previous phone, a single-SIM model (LG L70) running Android 4.4 KitKat, did not have this problem with the same SIM card.
I haven't found any setting anywhere in the UI that would control this, including using the search feature inside the Settings menu.
EDIT: I have just discovered that coming out of aeroplane mode also changes the language to Lithuanian.