I created test keys.
I understand your motivation, and know that this will preclude most people from using the app. Its akin to asking a gmail user to add pop3 and smtp servers, before they can send and receive emails.
Ideally you solution “autopilot” / outbox where the app is smart enough to figure out everything automagically. Specifying relays could be reserved for an unhappy path.
One of the things I am hearing from nostr users that have endured the pain and enjoy being here is that they dont have the patience to figure out specific purpose relay (e.g. for DMs).
Consider defaulting DMs relay for new users to one/a few DM relays like 0xchat relay, and importing DM relays for existing nsecs.
If existing nsecs dont have a relay DM, add whatever you think is best. Just dont wipe the relay list created in other apps.