This is because Kleopatra does not differentiate between invalid S/MIME and unverified OpenPGP certificates and we want to be able to encrypt to unverified OpenPGP certificates.

To proceed, I pushed an initial part as rG993820c31521: dirmngr: Factor out interrogate_ldap_dn function., which doesn't change any behavior.
Then, the point of the change will be clearer.

There is a reason why pcsc-shared is not the default ;-). Please try using Scute (best the t6002 branch until it has been merged) as pkcs#11 provider instead of pam_pkcs11. And you should of course use the stable version of GnuPG and not the LTS (2.2).

pinentry-emacs is obsolete. It's for older Emacs (<= 25, IIUC) which had lisp/pinentry.el.
For Emacs 26 and newer, you can simply use epa-pinentry-mode having the value of loopback.

Fix looks good to me. This could be tested with new long running test (tests/hashtest) that would allocate 4GiB+ pattern block for inputting to gcry_md_write.

This still did not seem to help me in making the tests working on Fedora with git master. I am still getting wrong paths to the gpgconf

gpgscm: error running '/root/gnupg/tests/tools/gpgconf': probably not installed

There is a full reproducer and more complete log in https://bugzilla.redhat.com/show_bug.cgi?id=2089075#c11

Yes I do understand Windows XP is not supported. Just in case it is a minor problem that is easy to fix and will not cost you much effort. I'd like to add more information: I do not change
%LOCALAPPDATA%. There is no such environment variable. A similar environment variable is:
APPDATA=C:\Documents and Settings\myname\Application Data
I do set GNUPGHOME=E:\key, which I think should be allowed because I do not want my personal info be stored in system drive.