Also described by @ReLater in #39774 (comment). This is an additional issue, that is significantly older (i suppose since the introduction of mail templates)

Steps to reproduce the issue

• Install joomla 4.2.6 or 4.2.7 with #39850 applied
• Make sure action logs for user events are enabled and configure working system email sending
• In the user settings for a user with a valid email address (you can receive mail on), enable user action information emails for the user component.
• Log out and log back in
• Look at the emails you should have received

Expected result

Plain text mails do not contain HTML links

Actual result

Plain text mails do contain HTML links, which renders weird in some mail clients

System information (as much as possible)

• joomla 4.2.7 on PHP 8.1
• Mail clients: e.g. Thunderbird, but also others

Additional comments

This appears to be a regression from the introduction of MailTemplates in Joomla 4.x and is working in 3.10.x

• All (default) mail templates are plain text in 4.2
• In 3.10.x, user information mails are rendered via the "normal" layout way - always producing HTML mails: administrator/components/com_actionlogs/models/actionlog.php#L167
• The data passed to the template did not change significantly between 3.10.x and 4.x, and still contains HTML markup in the bound values

This is a problematic situation, as the new mail templates also support HTML mails (that are disabled by default?), but there is no way to differentiate the values passed to the template. All simple fixes will lead to either the HTML emails losing the links, or to the plain text mails having HTML markup in them.