оно же из реп ставится и само решает

по карйней мере на 16.04.6 у меня всё так встало

Так я думаю будет понятнее:

zp-admin@zabbix-proxy-server:~$ sudo dpkg -i zabbix-release_4.0-3+xenial_all.deb                                                                       Selecting previously unselected package zabbix-release.
(Reading database ... 67007 files and directories currently installed.)
Preparing to unpack zabbix-release_4.0-3+xenial_all.deb ...
Unpacking zabbix-release (1:4.0-3+xenial) ...
Setting up zabbix-release (1:4.0-3+xenial) ...
zp-admin@zabbix-proxy-server:~$ sudo apt update
Get:1 http://repo.zabbix.com/zabbix/4.0/ubuntu xenial InRelease [7,096 B]
Hit:2 http://by.archive.ubuntu.com/ubuntu bionic InRelease
Hit:3 http://by.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:4 http://by.archive.ubuntu.com/ubuntu bionic-backports InRelease
Hit:5 http://by.archive.ubuntu.com/ubuntu bionic-security InRelease
Get:6 http://repo.zabbix.com/zabbix/4.0/ubuntu xenial/main Sources [1,184 B]
Get:7 http://repo.zabbix.com/zabbix/4.0/ubuntu xenial/main amd64 Packages [2,682                                                                        B]
Fetched 11.0 kB in 1s (7,994 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
11 packages can be upgraded. Run 'apt list --upgradable' to see them.
zp-admin@zabbix-proxy-server:~$ sudo apt install zabbix-proxy-mysql
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
zabbix-proxy-mysql : Depends: libcurl3 (>= 7.28.0) but it is not going to be in                                                                       stalled
                     Depends: libevent-2.0-5 (>= 2.0.10-stable) but it is not i                                                                       nstallable
                     Recommends: virtual-mysql-server
E: Unable to correct problems, you have held broken packages.
zp-admin@zabbix-proxy-server:~$

зачем sudo dpkg -i

libcurl3 я поставил руками, через sudo apt-get install

сделай apt install -f

он должен подтянуть зависимости... по идеи...

после установки zabbix-release неплохо бы apt update

делать

делал

чтобы бубунта узнала о том, что у ней появились репы

а из родных реп он что не ставится ? нафига через отдельный деб пакет ?

ну я тоже заббиксовую репу ставлю...

не знаю, почему(

apt search zabbix-proxy не ужели не находит пакет ?

zp-admin@zabbix-proxy-server:~$ sudo apt install zabbix-proxy-mysql
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
zabbix-proxy-mysql : Depends: libevent-2.0-5 (>= 2.0.10-stable) but it is not installable
                     Recommends: virtual-mysql-server
E: Unable to correct problems, you have held broken packages.

Упёрся в libevent

zp-admin@zabbix-proxy-server:~$ sudo apt install libevent-2.0-5
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libevent-2.0-5 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'libevent-2.0-5' has no installation candidate

без версии попробуй

и апдейт апгрейд ...