This is based on the respectve patch from NixPkgs, but with the parts pinning
mysql and postgresql executables removed. The our package definition on why.

diff --git a/src/akonadicontrol/agentmanager.cpp b/src/akonadicontrol/agentmanager.cpp
--- a/src/akonadicontrol/agentmanager.cpp
+++ b/src/akonadicontrol/agentmanager.cpp
@@ -61,7 +61,7 @@ public:
                 []() {
                     QCoreApplication::instance()->exit(255);
                 });
-        start(QStringLiteral("akonadiserver"), args, RestartOnCrash);
+        start(QLatin1String(NIX_OUT "/bin/akonadiserver"), args, RestartOnCrash);
     }
 
     ~StorageProcessControl() override
@@ -84,7 +84,7 @@ public:
                 []() {
                     qCCritical(AKONADICONTROL_LOG) << "Failed to start AgentServer!";
                 });
-        start(QStringLiteral("akonadi_agent_server"), args, RestartOnCrash);
+        start(QLatin1String(NIX_OUT "/bin/akonadi_agent_server"), args, RestartOnCrash);
     }
 
     ~AgentServerProcessControl() override
diff --git a/src/akonadicontrol/agentprocessinstance.cpp b/src/akonadicontrol/agentprocessinstance.cpp
--- a/src/akonadicontrol/agentprocessinstance.cpp
+++ b/src/akonadicontrol/agentprocessinstance.cpp
@@ -62,7 +62,7 @@ bool AgentProcessInstance::start(const AgentType &agentInfo)
     } else {
         Q_ASSERT(agentInfo.launchMethod == AgentType::Launcher);
         const QStringList arguments = QStringList() << executable << identifier();
-        const QString agentLauncherExec = Akonadi::StandardDirs::findExecutable(QStringLiteral("akonadi_agent_launcher"));
+        const QString agentLauncherExec = QLatin1String(NIX_OUT "/bin/akonadi_agent_launcher");
         mController->start(agentLauncherExec, arguments);
     }
     return true;
diff --git a/src/server/storage/dbconfigmysql.cpp b/src/server/storage/dbconfigmysql.cpp
--- a/src/server/storage/dbconfigmysql.cpp
+++ b/src/server/storage/dbconfigmysql.cpp
@@ -209,7 +209,7 @@ bool DbConfigMysql::startInternalServer()
 #endif
 
     // generate config file
-    const QString globalConfig = StandardDirs::locateResourceFile("config", QStringLiteral("mysql-global.conf"));
+    const QString globalConfig = QLatin1String(NIX_OUT "/etc/xdg/akonadi/mysql-global.conf");
     const QString localConfig  = StandardDirs::locateResourceFile("config", QStringLiteral("mysql-local.conf"));
     const QString actualConfig = StandardDirs::saveDir("data") + QLatin1String("/mysql.conf");
     if (globalConfig.isEmpty()) {
c0aba9ccfc346'>python</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/aux-files/python?id=7faf9df0d2d3cc575857bd10bcec0aba9ccfc346&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-04-14 21:01:34 -0400'>2023-04-14</span></td><td><a href='/guix/commit/gnu/packages/aux-files/python?id=3c8a4d64ffb9fe80ffbb32981bae72b0e690b0fa'>maint: Merge sanity-check-next.py into sanity-check.py.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/aux-files/python/sanity-check-next.py: Rename to...
* gnu/packages/aux-files/python/sanity-check.py: ... this.
* guix/build-system/pyproject.scm (sanity-check.py): Adjust file name.
* Makefile.am (AUX_FILES): De-register sanity-check-next.py.
</span></span></td><td>Maxim Cournoyer</td></tr>