The file(s) with .shasum extension are actually text files with one line for each other file that it contains the shasum for (or sha256sum as is the case here). Note that "sha256sum" is just a checksum created by essentially adding the bytes of the checked file with some maths juggling so that the final "number" is a kind of fingerprint for it. Basically any change to the checked file would result in a different fingerprint.

So the .shasum file just tells what the checksum of the checked file(s) is supposed to be. You wouldn't really compute the sha256sum of those .shasum files... unless I suppose you want to compare different downloads of those .. and then "diff" or "cmp" would work as well.

The ISO devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso has its sha256 sum recorded in devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum

I don't know the details of devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso which is something different.

I have deleted the netinstall iso but kept a text file for its shasum:

$ shasum devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum
2c3bacb5bf172982f9295b6450da103e63930ef73db91d553e0d9fd48410ed9c  devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum

$ sha256sum devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum
2c3bacb5bf172982f9295b6450da103e63930ef73db91d553e0d9fd48410ed9c  devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum

In the release archive, various folders for Daedalus do not have the same structure as those for other releases, there are no general SHASUMS.txt or SHASUMS.txt.asc but individual shasum for each iso.
This is why I thought I was going to check the iso shasum against the individual shasum downloadable for that very iso.

I don't know the details of devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso which is something different.

The file ...shasum contains the sha256sum; you don't run sha356sum on it. E.g. download both, then run

sha256sum -c devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum

Note the -c.

Thanks for your help.

this is what I have got back:
$ sha256sum -c devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso
sha256sum: devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso: no properly formatted SHA256 checksum lines found

$ sha256sum -c devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso.shasum
sha256sum: devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso.shasum: No such file or directory

$ sha256sum -c devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso.sha256
devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso: OK

Yes, they are, I have been checking again

sha256sum -c devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum

Note the -c.

Being a Devuan user for years, running various installations of Chimera and wanted to test Daedalus today, I came accross some discrepancies regarding various shasums for Daedalus.

I wanted to try devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso for which I got the following sha256sum: 8577f535c62d3091bcd9ad5494ef007bc3b5c359bd22c5ea5800f1d29e2a6d9a

but the sum for devuan_daedalus_5.0.preview-20230515_amd64_netinstall.iso.shasum is the following:
2c3bacb5bf172982f9295b6450da103e63930ef73db91d553e0d9fd48410ed9c

So, I have experimented with various repos, only to get the same discordant results.

Searching on the forum, I came accross this post : https://dev1galaxy.org/viewtopic.php?id=2697

I went on downloading the minimal live iso, as the netinstall iso was dated from May 15th and today we are the 16th:

devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso
shasum: 21a8306886343ecb53e4327d203772dabd99618cb8e7f28f24f6784dfcac08ef

when devuan_daedalus_5.0.preview_20230502_amd64_minimal-live.iso.sha256
is 23edceaf1f96bc411e137f04ba4b1c20c1cf3dff5827dad7aecfc10641d8e393

I am a bit lost there, could somebody tell me what is wrong?
Thanks a lot