Task 'prep_talk' fails with php declare error

[0xphk]

The 'install talk app' step in the tasks fails with following error message:

The system is Ubuntu Server 18.04

stderr: 'PHP Fatal error: Cannot declare class OCA\Talk\Migration\Version2000Date20170707093535, because the name is already in use in /var/www/nextcloud/apps/spreed/lib/Migration/Version2000Date20170707093535.php on line 127'

As I'm not really used to php, any help would be appreciated.
Thank you

[0xphk]

Might be related to this: nextcloud/spreed#2806

[0xphk]

Only way for a successfull install is to keep 'talk_install' option set to false.
Talk can be installed later via Webinterface, which gives the same above errormessage,
but install is successful and Talk works as intended.

[ReinerNippes]

seems to be fixed with nc19.
since it's a native nextcloud problem it's beyond my scope. sorry.
https://help.nextcloud.com/t/cannot-install-talk-on-fresh-nextcloud-18-install/68613