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pinentry-emacs is obsolete.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.

We should close this. The recent fix in 2.2 and the forthcoming 2.3 does everything we want. In the meantiime or if further problems turn up, --ignore-cert is a good workaround.