[Bug]: Legacy version for macOS cannot be installed

[fuzzykiller]

⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

When trying to install the macOS client legacy version, an error appears:

“Nextcloud-2.6.5.20200710-legacy.pkg” can’t be opened because Apple cannot check it for malicious software.

This is apparently caused by the notarization info on this file is too old or something. I’m not a macOS developer, sorry if the terms are inaccurate.

# spctl -a -vvv -t install Nextcloud-2.6.5.20200710-legacy.pkg 
Nextcloud-2.6.5.20200710-legacy.pkg: rejected
source=Unnotarized Developer ID
origin=Developer ID Installer: Nextcloud GmbH (NKUJUXUJ3B)

Steps to reproduce

Download legacy client from Nextcloud homepage, attempt to open the .pkg file.

Expected behavior

Client should install.

Which files are affected by this bug

n/a

Operating system

Mac OS

Which version of the operating system you are running.

11.7.9 (20G1426)

Package

Other

Nextcloud Server version

latest aio

Nextcloud Desktop Client version

2.6.5

Is this bug present after an update or on a fresh install?

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

No response

Additional info

No response

[joshtrichards]

See #6179 step 2 in the reproduction steps for how to address that.

There's only so much that can be done about legacy clients which aren't even officially supported...