I do not know if the solutions I listed below are open source ; however as an open source contributor I am used to work with some tools depending to choice of the projects:
About credits, I don’t think these tools exposes in some automated way the contributors identities. However, nothing prevents you to use these web UI tools to find who contributed and list people for example in your CONTRIBUTORS files. Another way could be to edit the automated commits these tools submit to your Git repos by adding credits to the translators (with for example Co-authored-by field).
It is complicated. He says true. And maybe your need to use GrapheneOS is relevant. If you have a smartphone without cellular connection, for a daily usage, FMPOV it is a non-sense in case of emergency. It is a risk you will have to take, I can’t disagree your dad. And what about your solution but with a SIM card with very few data and SMS available, through a SIM card you can keep aside your phone and insert when needed?