How to migrate from Owncloud > 10.0?

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1

I’m trying to migrate from Owncloud 10.2.1.4 to Nextcloud 12.
According to https://docs.nextcloud.com/server/18/admin_manual/maintenance/migrating_owncloud.html
a jump between these versions is possible
10.0.1 or later 12.0.x (but at least 12.0.1)
Although there is no mention of versions higher than Owncloud 10.0.x on https://nextcloud.com/migration/
ownCloud 10.0.x is compatible with Nextcloud 12.0.x

Now I’ve tried to do the upgrade according to the documentation and I get the following error:
Updates between multiple major versions and downgrades are unsupported.
I’ve checked the upgrade code and If I’m not wrong the problem is that there’s no mention of Owncloud higher than 10.0.x in the version.php file:

  'nextcloud' =>
  array (
    '11.0' => true,
    '12.0' => true,
  ),
  'owncloud' =>
  array (
    '10.0.0.12' => true,
    '10.0.1.5' => true,
    '10.0.2.1' => true,
    '10.0.3.3' => true,
    '10.0.4.4' => true,
    '10.0.5.4' => true,
    '10.0.6.1' => true,
    '10.0.7.2' => true,
    '10.0.8.5' => true,
    '10.0.9.5' => true,
    '10.0.10.4' => true,
    '10.0.11' => true,
    '10.0.12' => true,
    '10.0.13' => true,
    '10.0.14' => true,
    '10.0.15' => true,
    '10.0.16' => true,
    '10.0.17' => true,
  ),
);

If this is indeed the problem how should I try to migrate?
Are newer Owncloud Versions unsupported? Should I try to manually adjust the updater to allow the update like in multiple threads refering to Cannot manually upgrade from 11.0.3

Would be great if someone could help me out here.

Edit: As an additional note the vendor in the database is set to Owncloud and it’s set to Nextcloud in the versions.php

2

There are a few asking to update this: https://github.com/nextcloud/owncloud-web-migrator/issues

In the past, this was upgraded from time to time, @jospoortvliet perhaps knows when the next time is planned.

You can try yourself with different versions of Nextcloud, I think the developers are the only ones who can probably say what might work. You need to do some testing to be sure that there is nothing broken.