Skype is still supported in Linux?
But I heard that it is dieing soon,
at least on mobile phones,
because it can't compete with Whatsapp, Line, Wechat etc.

where did you "hear" that Skype is dying?

For me, Skype died because it didn't work on my Linux box. But others are apparently using it with varying degrees of success. The Linux version of Skype has traditionally been several releases behind the Windows version. What would you expect? Microsoft owns Skype!
Never heard of any of those.

Skype may be one of the most popular apps for it's use. It has a number of features that make it relevant.

Not sure about some of those applications, but skype is certainly not going anywhere. I use line, but the longer I have it, the more I hate it. People send dumb stickers, line sends invitations to games, does not do video calling, or i never tried.

But skype integrates nicely with the phone. I have multiple numbers people can call and I can call just about any landline in the world for free. Without having to start skype.

Many people use skype in that way so i am confident it aint going nowhere

For mobile, Whatsapp is the best but it can make call.
Wechat is the most popular in Asia, China.
Wechat can make call and video call.
Viber is losing steam, Viber makes your phone run slower and hanged.

I also have ICQ, it is good to link with Facebook's contacts.

Whatsapp and other text message programmes is not the same as skype.

Skype is the winner of the bunch because when i say call, i am not talking about only calling other users of the same software. Using skype it integrates with the phone in the sense that it will allow you to place a call to a real telephone when you dial using the default touchpad for your phone. So when you want to call grandma that has no computer or anything like that.

Skype also provides a service to call landlines world wide, voicemail from normal telephone users, call waiting and call forwarding.

So these programmes are not quite the same or meant for the same target market. Now sure something new at times may be fun for a while, but i surely cannot rely on those apps to let family back home call me on a local number in their country or business partners overseas to call me directly on my phone without paying international rates.

That is the area where skype shines through.

Sure you can setup your own pbx instead, but hassle vs cost for only a single user... i think skype is the better choice among these.

viber makes my phone slow, I had undeleted it.