As discussed here, .IsNode should be false for the 404.html template.

What version of Hugo are you using (hugo version)?

$ hugo version
hugo v0.123.3-a75a659f6fc0cb3a52b2b2ba666a81f79a459376+extended linux/amd64 BuildDate=2024-02-23T17:09:20Z VendorInfo=gohugoio

Does this issue reproduce with the latest release?

Yes