Latest 12.2 and indeed, it does show delivered... Probably to some other device which is online not my friend who is roaming in germany somewhere... So I guess that's the issue..
It's very annoying iMessage is linked to the sim card, and doesn't use a more flexible system like whatsapp, which allows you to use the same number even if you switch sim cards temporarily.
I find the ONLY way to force send as SMS without screwing with disabling ... which requires you to RE-Initiate iMessage registration once it turns back on again ... is when you're out of any network connectivity. You send an iMessage which fails and is paused until network connectivity is re-initiated, and before that occurs tap and hold the send icon and you have send as sms ... yet will only work once you of carrier connection ... so initially it'll fail yet hold and then you send and it'll goto SMS.
It's very annoying iMessage is linked to the sim card, and doesn't use a more flexible system like whatsapp, which allows you to use the same number even if you switch sim cards temporarily.
Yes, but you can't keep them linked unless your sim remains active. And once a thread starts with a phone number, you can't switch. So if someone starts a conversation on your phone number, and you swap sims, those messages will stop coming. Unless you send them another message first from your iCloud account.