upgrading ubuntu mate from 16.04 to 18.04 on powerpc

Description: Ubuntu 16.04.5 LTS
Release: 16.04

ubuntu-release-upgrader-core (1:16.04.25)
ubuntu-release-upgrader-gtk (1:16.04.25)

The problem occurred on Power Mac G5 Quad.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.25
ProcVersionSignature: Ubuntu 4.4.0-134.160-powerpc64-smp 4.4.140
Uname: Linux 4.4.0-134-powerpc64-smp ppc64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: powerpc
CrashDB: ubuntu
Date: Fri Sep 7 19:43:12 2018
InstallationDate: Installed on 2018-09-02 (5 days ago)
InstallationMedia: Ubuntu-MATE 16.04.1 LTS "Xenial Xerus" - Release powerpc (20160719)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=ru
 PATH=(custom, no user)
 LANG=ru_RU.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2018-09-07 (0 days ago)
VarLogDistupgradeAptlog:
 Log time: 2018-09-07 19:42:29.561599
 Log time: 2018-09-07 19:42:32.859177
 Log time: 2018-09-07 19:43:08.986852
 Log time: 2018-09-07 19:43:16.602452
VarLogDistupgradeTermlog: