Afternoon, all.
I've had a sneaking suspicion that this was going to happen for long enough. And, as if to prove me right, it has.
--------------------------------
There's always been a plethora of 'chat clients' around......but never that many which would work under Linux. In recent years, the majority of the latter have changed the method of operation; if you want to use their desktop client, you MUST already be running it as a smartphone app. All the desktop client will do is "pair" with the mobile app. It's got to the stage where the mobile device is now the primary target; the PC desktop (tower or laptop) is very much the poor relation, and relegated to the status of 'secondary' or 'backup' device.....
How times change, huh..?
Until very recently, Telegram has been pretty much unique, in that although you still need a phone for logging-in or creating an a/c, all Telegram has ever used your number for is to send you a 5-digit confirmation code via SMS, to be entered into the desktop client when requested. Thus, it doesn't need to be a smartphone; a 'dumb' phone would work just as well. If you stay permanently logged-in, you would never need this anymore, I suppose; as it is, you get sent a fresh one of these codes every time you log-out & sign back in again.
Well, not any more. New ownership has meant the "new broom sweeps clean"; out has gone the old, favoured way of doing things, to be replaced by the exact same way of logging-in as every other chat client out there. If you want to log-in to your a/c on a desktop or laptop, you've got to have a second device beside you, also running Telegram, with you already logged-in on it.....because sign-in codes will only be sent, in-app, to 'another Telegram device'. SMS has been consigned to the giant tech waste-bin in the sky, as far as this goes.
So; what do you do if, like me, you refuse to be pushed into 'conforming' with the herd? I don't possess a smartphone....or a 'pad' of any sort. I have neither use for, nor need of them. But it's getting so if you want to do just about anything online these days, you will before too long have no option BUT to buy a smartphone, whether you want to or not. Everything is being written & coded for these infernal gadgets, with that development being prioritised over everything else......
------------------------------
Short-term, at least, there IS a 'workaround' for anyone running Telegram; a small group of devs have forked one of the last versions of Telegram before this 'in-app' login became fact about 2 months ago. It's called
Kotatogram
.....and still permits SMS code logins. So, quite simply:-
Fire-up the Kotatogram fork & sign-in with that; leave this running. Now fire-up the real Telegram, go through the sign-in process , and when you've given it your phone number it now sends your sign-in code to "another Telegram device". Look over at the 'fork'.....and there will be your 5-digit code. Sign-in with Telegram, and you can then close the other one down.
It's only possible to have TWO 'Telegram devices' running on one computer because they're not actually the same app (you can't do this with two instances of Telegram itself, 'cos it won't have it). And it's nothing to do with config files, because Telegram doesn't generate any.....all config stuff lives in the cloud, essentially accessed only via randomly-generated remote codes, a la 2FA. I guess this is all recognised via hostnames and MAC codes/IP addresses.
-------------------------------------------------------
I know, I know; it's a bit long-winded doing it this way. However; what I've done is to supply the Kotatogram 'fork' as a portable; this can live on a flash drive, and just be brought out as & when it's needed.
For anyone who wants to take a look at this, you can find the Kotatogram tarball here:-
https://mega.nz/folder/vOohwAaJ#SScDuHUxITAEgrjQGe0jew
I don't recommend using this full-time; the updater doesn't work, and you can't keep up with the latest Telegram versions because they only built the one release of this.....more or less with the intention of it being used along these lines.
Anyways; hope it's useful for some of you.
Mike. 
