I have fully described the problem here:
https://www.reddit.com/r/openSUSE/comments/b6v3yq/there_is_no_possibility_to_use_system/

Short: telegram does not allow you to enable system notifications in the
openSUSE tumbleweed KDE Plasma 5.

Output on startup:
QNetworkReplyImplPrivate::error: Internal problem, this method must only be
called once.

QNetworkReplyImplPrivate::error: Internal problem, this method must only be
called once.

QNetworkReplyImplPrivate::error: Internal problem, this method must only be
called once.

Bug ID	1131010
Summary	server:messaging/telegram-desktop: Bug
Classification	openSUSE
Product	openSUSE.org
Version	unspecified
Hardware	Other
OS	Other
Status	NEW
Severity	Normal
Priority	P5 - None
Component	3rd party software
Assignee	nix@opensuse.org
Reporter	vitalykorotkov@openmailbox.org
QA Contact	bnc-team-screening@forge.provo.novell.com
Found By	---
Blocker	---