Changes have been made in Git (FRAMEWORK_6_0):

commit 92ada4983862eb8cc2bab76b63a8cf2ea7d71c87
Author: Ralf Lang <ralf.lang@ralf-lang.de>
Date:   Sat, 07 Mar 2026 21:17:07 +0100

feat(mysql): add TEXT/BLOB/JSON default value expression support

Port critical bug fix from lib/ (Bug #15172) to src/. MySQL 8.0.13+
requires TEXT, BLOB, JSON, and GEOMETRY column defaults to use
expression syntax: ('value') instead of 'value'.

Changes:
- Add filterDefault() method to Mysql/Schema to wrap defaults in
   expression syntax for affected column types
- Update Base/Schema addColumnOptions() to detect and skip quoting
   expression defaults (strings starting with "('\'' and ending "\')")
- Apply filter in makeColumn() when creating Column objects
- Apply filter in changeColumn() by passing $typeSql to addColumnOptions()
- Add 20 unit tests in SchemaDefaultsTest covering all column types
- Add 10 integration tests (requires MySQL 8.0.13+, currently skipped)

This prevents SQL syntax errors when setting defaults on TEXT/BLOB/JSON
columns in MySQL 8.0.13+ and MariaDB 10.2.1+.

Related: Tasks 1.1-1.6 from db-bug-fixes-todo.md

  M src/Adapter/Base/Schema.php
  M src/Adapter/Mysql/Schema.php
  A test/Adapter/Mysql/ExpressionDefaultIntegrationTest.php
  A test/Adapter/Mysql/SchemaDefaultsTest.php

https://github.com/horde/Db/commit/92ada4983862eb8cc2bab76b63a8cf2ea7d71c87

Closing as resolved by https://github.com/horde/Db/releases/tag/v3.0.0alpha6

Changes have been made in Git (FRAMEWORK_6_0):

commit 9b12019057d6b5dd3b9a488598256e554e77a136
Author: Ralf Lang <ralf.lang@ralf-lang.de>
Date:   Thu, 29 May 2025 12:49:21 +0200

Release 3.0.0-alpha6  (API Version: 3.0.0-alpha1)

fix: Also apply defaults filter when changing an existing column's type
fix: Special case default field values must not be quoted if they are 
expressions
feat: Optionally supply sqlType to addColumnOptions
fix: #15172 Add a filter to support column defaults on mysql >= 8.0.13 
for TEXT, BLOB and JSON format

  M .horde.yml
  M composer.json
  M doc/changelog.yml

https://github.com/horde/Db/commit/9b12019057d6b5dd3b9a488598256e554e77a136

Preliminary patch at library level

commit c2d525d02cb0a7c2f087e0c86f9728caf3e44816 (HEAD -> 
FRAMEWORK_6_0, origin/HEAD, origin/FRAMEWORK_6_0)
Author: Ralf Lang <ralf.lang@ralf-lang.de>
Date:   Thu May 29 11:08:19 2025 +0200

     fix: #15172 Add a filter to support column defaults on mysql >= 
8.0.13 for TEXT, BLOB and JSON format

Will test if this is sufficient for nag and kronolith on this version of mysql

Confirmed.
I don't have this in mariadb.
There's a workaround in mysql 8.0.13 and later by using an expression 
rather than a literal as default for text and blob field. We will 
build a patch based on this.

Fresh install according to:
https://wiki.horde.org/Doc/Dev/H6/Installation/InstallBase?referrer=Doc%2FDev%2FH6%2FInstallation

The execution of
http://192.168.122.5/horde/admin/config/?app=kronolith&action=schema
throws the above error.

The schema remains without update.

IMHO the problem seems to be located in
/var/www/html/horde/vendor/horde/kronolith/migration/28_kronolith_icalendar_storage.php
line 46.

IMHO related to:
https://www.percona.com/blog/cant-we-assign-a-default-value-to-the-blob-text-geometry-and-json-data-types/