Has now been backported to be released with 2.2.53

It looks like we get a specific "Invalid public key algorithm" error from gpgme so that we can add helpful information with likely reasons to the error message.

I might add that we recently had a customer support contact where they had that error and asked how they could make using their S/MIME certificates work.

The behaviour might have changed a bit because of the ldap: prefix i use now, or i have missed this case the last time:
Given some cert on the "download" server, I can find it, if dirmngr.conf contains only the "download" server, or if the "download" server is listed first:

Independent of keyserver order in dirmngr.conf, --search-keys still offers keys from the upload server, but the download fails:

For "Although the upload server is used for upload, the gpg message still displays the first keyserver" see T8025

That was fixed with 2.2.52 which fixed a bug in the fix done in 2.2.50 (see rG31fef13df1). Note that 2.2.48 to 2.2.50 had only internal releases.

The problem was the keyserver configuration, which does not include a scheme (ldap:):

keyserver ldap.gnupg.test:389:uid=LordPrivySeal,ou=GnuPG Users,dc=gnupg,dc=test:pass:dc=gnupg,dc=test:

Well, I tested this again. I created a new key and saved a copy. The I updated the expiration date to 2035 and sent the key to the LDAP server. Then I deleted the updated key locally and imported the old copy. Thus I have now:

we haven't seen this in a while…

This seems not to work in Kleopatra/gpg in gpg4win-5.0.0-beta413 @ win11.

Tested on gpg4win-5.0.0-beta413 @ win11 with the following entries in dirmngr.conf:

meanwhile it looks like this in Kleopatra, it has now the blue sign but the issue is still the same:

Looks good to me on gpg4win-5.0.0-beta395 @ win11 (gpg 2.5.13).