I use 2 SIM-Cards with my FP2 under Android 6.0. When I turn off one of these SIM-Cards and turn it on again, the settings are lost. I want, that the phone asks me which SIM I want use to make a phone call or send an SMS (in that cases, where both SIM-Cards are turned on). Every time I switch off…

FP2 should remember SIM-Settings in Dual-SIM Mode

BertG October 11, 2017, 2:18pm 3

That can be done by using an app.
Maybe you will find some hints in this thread:

and of course by searching for “Dual SIM” in the play store (i.e. Yalp via F-Droid in my case).