zabbix server fails to read database after upgrade

[ptera]

After upgrading ubuntu to Ubuntu Linux 20.04.6 - zabbix server crashed. Had to backup database and start over.
After installing zabbix-release_6.0-1+ubuntu20.04_all.deb my zabbix-server fails to start with the following error.
After restoring the backup and setting permissions...

250818:192120.155 database connection re-established
97325:20250818:192120.158 The server does not match Zabbix database. Current database version (mandatory/optional): 05000000/05000007. Required mandatory version: 04000000.

Help appreciated - we are a large WISP and are blind - not able to monitor for down equipment.

[ptera]

OK I see the database is 050... I just tried to upgrade to zabbix-release_5.0-1+bionic_all.deb
and got
The following packages have unmet dependencies:
zabbix-server-mysql : Depends: libevent-2.1-6 (>= 2.1.8-stable) but it is not installable
Depends: libmysqlclient20 (>= 5.7.11) but it is not installable
Depends: libsnmp30 (>= 5.7.3+dfsg-1.8ubuntu3.6~dfsg) but it is not installable
E: Broken packages

[cyber]

backup seemed to restore v5 DB (mandatory/optional): 05000000/05000007) but seem you managed to install v4 Zabbix (Required mandatory version: 04000000)?

I would never upgrade OS under working application, better to prepare new side-by-side platform and migrate application... It seems like you are trying to install now older Zabbix on newer platform which does not support it... Seems like you need a host, which has whatever OS version you had before upgrading... and try to restore there.

[ptera]

Ok I had to trash and start over. I exported all my hosts and templates before hand. When I try to import them into 7.4.1 I get an unhelpfull error.
Invalid parameter "/55": value (uuid)=(3598da1effdf4ed48074608f1422e3fd) already exists.
It is a very large file.
I am trying to figure out how to cut it into sections but I keep getting the jason format error.
Can some one point me to what is the proper JSON file format?

[ptera]

Ok for my closing - I installed everything new on a different server and tried to upgrade the database 5000000 to 6000000 using instructions from zabbix at

https://www.zabbix.com/documentation/6.0/en/manual/appendix/install/db_primary_keys#mysql

I got to running "util.exportTable("history_old", CSVPATH + "/history.csv", { dialect: "csv" });" in mysqlsh
First exportTable was unknwown command replaced with export_table
Second 'dialect' was undefined name.
I gave up...