Can't install UML Designer 8.1 from Eclipse Marketplace

[RIAMCode]

When pressing the "Install" button, there's an error saying "The following solutions are not available: UML Designer 8.1".
Looking at the error log, it seems like the key https://s3-eu-west-1.amazonaws.com/obeo-networkaggregation-releases/sirius_5_1 isn't available.

`eclipse.buildId=4.30.0.20231201-1200
java.version=17.0.9
java.vendor=Amazon.com Inc.
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=fr_FR
Framework arguments: -product org.eclipse.epp.package.jee.product
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product

org.eclipse.epp.mpc.ui
Error
Wed Jan 31 10:25:18 CET 2024
The following solutions are not available: UML Designer 8.1 (id=org.obeonetwork.dsl.uml2.runtime.sdk.feature.feature.group, site=https://s3-eu-west-1.amazonaws.com/obeo-networkaggregation-releases/sirius_5_1/)
`