The legitimate reason is that the domain is correctly classified as having user generated active content, because the Immich GitHub repo allows anyone to submit arbitrary code via PR, and PRs can be autodeployed to this domain without passing review or approval.

Domains with user generated active content should typically by listed on Mozilla's Public Suffix list, which Firefox & Chrome both check & automatically apply stricter security settings to, to protect users.

> correctly classified as having user generated active content

No it's not

> PRs can be autodeployed to this domain without passing review or approval.

No they can't

There is no untrusted/user content on these domains.