Just updating situation on migration/upgrate.
My investigations of my problem revealed to me a reason why any update from 8.2.x is failing again and again.
In short words, something was changed in ‘./occ upgrade’ script and now in 9.x+ versions of OwnCloud and NextCloud this script performing some kind of work with LDAP-user accounts and upgrade stucks in one of the steps. Not sure what step actually lead to stuck whole upgrade but think this happens on processing shared files(folders)
Repair unmerged shares
Starting …
3502/58276 [=>--------------------------] 6%
Workaround:
Before upgrade from 8.2.x to next Major Release you need to disable user_ldap app with CLI command
sudo -u www-data php nextcloud/occ app:disable user_ldap
I will test it further if there are some kind issues after upgrading with disabled LDAP-accounts, how it influences to user shares. But disabling user_ldap app is only way to get updated at this moment.
And all written above is applied to any further updates after 9.x. So to update from 9.x to next stable I need to disable user_ldap again, and from 10 to 11 too.