so, why i choose xmpp and sip ?

instead of going on whatsapp, telegram, signal..

firstly, what are those two protocols?

SIP is a protocol to do phone communications over the internet. Eg, Linphone is both a client/application/software (computer, phone), but also a SIP service provider. Both can be dissociate : you can use linphone service with a hardware sip phone. You can use linphone software or app with different/multiple providers (even not linphone)

xmpp is a protocol to communicate through internet : secured messages, plus voice/video. Like SIP. Conversations and quicksy are the most recommended xmpp client/application for android. You can find Monal on iPhone, Gajim and Dino for windows, macos, linux, unix.

to compare, if you didnt understood : imap and smtp are making emails services works. without imap/smtp, you just can't use emails. (i exclude mapi/exchange to not complicate things)

alice@first.net is an email. it can be also also be a SIP address, or xmpp one. it's called an URI. bob@conversations.im is not an email. it's bob's xmpp address (or URI)

then, why xmpp or sip, where others exists too?

hey, that's a gift : https://paste.debian.net/hidden/732389ee/

TBH, on my own : i just dont understand how to be “okay” with using those big messaging tools. I dont.

if relatives are not happy, a text message (sms) or an email, still works. Yep, technology-type prevails on the contact. Yep. Some people are proud to be “grammar-nasi”, for me it's the technology, and i wont change for your eyes :)

i tried to do my best writing this, if you want to correct errors..

hello,

No, as always replied : i wont have whatsapp, nor yesterday, not today, not more tomorrow. only alternative to whtasapp me : to transmit me the device, with the sim card inserted and the application installed, through post mail, ready to use, obviously at fees or charges of the person whom wants to reach me on it, with a dedicated phone, of course. I wont spend a penny for it, never.

my private phone number wont be, even for “a million eur/usd”, reachable on whatpp. Decision will change for nobody.