Do you see something similar to the following?
2023-10-24T11:39:17 [I|app|8dce6478] Started GET "/userdata/user-data?url=<foreman URL> for <host IP> at 2023-10-24 11:39:17 +0200
2023-10-24T11:39:17 [I|app|8dce6478] Processing by UserdataController#userdata as TEXT
2023-10-24T11:39:17 [I|app|8dce6478] Parameters: {"url"=>"<foreman URL>", "userdatum"=>{}}
2023-10-24T11:39:18 [I|app|8dce6478] Rendered text template (Duration: 0.0ms | Allocations: 1)
2023-10-24T11:39:18 [I|app|8dce6478] Completed 200 OK in 506ms (Views: 1.0ms | ActiveRecord: 65.8ms | Allocations: 76581)
There might be also some calls to userdata/vendor-data but those can be ignored.
The associated templates are fine. So, for further debugging, please post the rendered version of the Preseed default PXELinux Autoinstall and Preseed Autoinstall cloud-init user data templates 