Replace them with a stub as discussed in #168480 (comment), so that fs-repo-migrations still finds the binaries in the PATH and never attempts to download these binaries from the internet, because that is a bit uncool.

this fails because ld-linux.so is missing

If anyone still wants to actually use these migrations, they should use an old version of Nixpkgs that still includes Go 1.16.

not practical, as this will compile go_1_16 = slow

the fix is as simple as ipfs/fs-repo-migrations#163

this fails because ld-linux.so is missing

From reading what you linked to, it sounds like you ran ipfs daemon with a repo, which required a migration. The migration binary fs-repo-11-to-12 was not in the $PATH, so Kubo downloaded it off the internet, which then failed to run. It doesn't surprise me at all that random binaries off of the internet don't work on NixOS because NixOS does not implement the FHS. As such I don't think the downloaded binary not working on NixOS is an issue in Kubo. Please make that clear in the linked issue.
Kubo would not have tried to download a binary if you had put kubo-migrator-all-fs-repo-migrations into its $PATH. I replaced all the old migrations instead of deleting them to try to prevent such a situation.
Anyways, my comment only mentions fs-repo-migrations, which you did not run and so I don't understand what your comment is about. Did I understand something incorrectly?

not practical, as this will compile go_1_16 = slow

This is not true, everything is still in the cache. To test for yourself:

git checkout 4c3c80df545ec5cb26b5480979c3e3f93518cbe5
nix-build -A ipfs-migrator

I got this commit hash from the list at https://channels.nix.gsc.io/nixpkgs-unstable/history. The timestamp is from a day before Go 1.16 was removed.

the fix is as simple as ipfs/fs-repo-migrations#163

Thanks, I will try to incorporate this patch into this PR when I have some time.
You only fixed the 10-to-11 and 11-to-12 migrations. What about the older migrations? Can they not be fixed in the same way or would it be more effort?

What about the older migrations?

see my PR

From reading what you linked to, it sounds like you ran ipfs daemon with a repo, which required a migration.

yes

The migration binary fs-repo-11-to-12 was not in the $PATH, so Kubo downloaded it off the internet, which then failed to run.

i run

nix-shell -p ipfs kubo-migrator # aka: ipfs-migrator
which fs-repo-migrations
# /nix/store/af47hh83i6awalxhrfdpr40gks5cm0fi-kubo-migrator-2.0.2/bin/fs-repo-migrations
ipfs daemon

so ipfs should use fs-repo-migrations

it works with

nix-shell -p ipfs kubo-migrator-all-fs-repo-migrations
which fs-repo-11-to-12
# /nix/store/60fnfclibg8mn0f0s55yv6v07dz7vh4c-kubo-migrator-all-fs-repo-migrations-12.1.0.2/bin/fs-repo-11-to-12
ipfs daemon

Ok, it should work now, thanks again for the patch.
I had to create a separate derivation for the source. This is because I'm using using sourceRoot inside the derivation which builds the individual migrations and that would otherwise require me to change the patches to apply to the child directories instead and to apply each patch only to the corresponding migration. Using a separate derivation just for patching is easier.

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-already-reviewed/2617/850