Select "Move to Focused Inbox", choose "Move this and all future messages ... Always show content." Open your Mail app and go to the Mailboxes screen. Select the Junk folder. Find the email you want ...

Scroll down and tap Settings. Tap on your email address under the "General settings" heading. Hit "Inbox type" and select ...

Until iOS 18.4, the Mail app would always automatically move on to the next message in the inbox, which would annoyingly cause that unrelated message to be marked as read in the process.