This is not the case. The forum reports were about a different Nextcloud bug introduced with TOS 6 which was promptly identified and fixed in TOS 6.0.2.
Your issue is related to the fact that Nextcloud can’t connect to the database, either because it’s not running or it hasn’t been installed/configured (properly). Same as @mvasilek above I wasn’t able to reproduce your issue by installing NC on TOS 6.0.4 and I don’t see any other related reports. Likely it is an individual problem you are encountering.
You can fix the ‘not running’ issue quite easily by issuing the following two commands:
/etc/init.d/mysqld enable
/etc/init.d/mysqld start
If that results in an error message or doesn’t fix the problem I suggest uninstalling and then reinstalling Nextcloud. Backup any Nextcloud data first.