Nearly successful Upgrade 5.6.1 -> 5.8.1 (database issue)

I hope my notes would be useful

During upgrade I had an issue with database upgrade

Mysql2::Error: Incorrect string value: ‘\xD1\x83\xD0\xB4\xD0\xB0…’ for column opennebula.vm_pool.short_body at row 1
/var/lib/gems/2.3.0/gems/mysql2-0.5.2/lib/mysql2/client.rb:131:in _query' /var/lib/gems/2.3.0/gems/mysql2-0.5.2/lib/mysql2/client.rb:131:inblock in query’
/var/lib/gems/2.3.0/gems/mysql2-0.5.2/lib/mysql2/client.rb:130:in handle_interrupt' /var/lib/gems/2.3.0/gems/mysql2-0.5.2/lib/mysql2/client.rb:130:inquery’
/usr/lib/ruby/vendor_ruby/sequel/adapters/mysql2.rb:80:in `block in _execute’

I’ve read opnnebulas’ bugreport and linked articles. In the end I’ve solved it by tuning database

ALTER DATABASE databasename CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE opennebula.vm_pool CONVERT TO CHARACTER SET utf8;

I’m not sure, but I decided to convert all tables in database:
SELECT CONCAT(‘ALTER TABLE ', TABLE_NAME,' CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;’) AS mySQL
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA= “opennebula”
AND TABLE_TYPE=“BASE TABLE”;

My Database server is MariaDB 10.4.6 (xenial) with Galera Cluster