[debian-mysql] Bug#1031860: libmariadb3 seems to be the culprit

[Andreas v. Heydwolff]

A solution suggested here when the problem appeared fixed the problem 
for me:

   https://codereview.qt-project.org/c/qt/qtbase/+/363880

--- quote ---
MySQL: remove the version number checks in favor of actual functionality

MariaDB library version 3.2 no longer returns the server version in the
10.x range but the library version itself, which is lower than 4.x. That
meant we concluded the server did not support prepared statements.

And because of the lack of prepared statements, all QDateTime
conversions failed, because of the timezone. I don't know if this was
intended or what, but it's a side issue.

[ChangeLog][QtSql][MySQL] Fixed the detection of whether the client and
server support prepared statements. This was caused by the mariadb
connector library reporting its own version numbers (starting in version
3.2) instead of the server version.
--- quote ---

I replaced

   libmariadb3_1%3a10.3.38-0+deb10u1_amd64.deb

with

   libmariadb3_1%3a10.3.36-0+deb10u2_amd64.deb

and now everything is functional again although the mariadb client and 
server packages are all at 10.3..38.

I'm not a programmer and have no ide where to fix this, but for now 
pinning libmariadb3 at v10.3.36 does the job.

Best,
Andreas