SUMMARY
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Dolphin does not open with the previous tabs after restart.  Option to do that ("Folders, tabs, and window state from last time" at "Show on startup", Dolphin Preferences Dialog) is selected.
It worked OK until previous version/release, before 2023 May 14th.

STEPS TO REPRODUCE
1. Open 2 or more tabs, each one with a different folder (for example "/etc" in one and "/home" in the other)
2. Click "Settings → Configure Dolphin..." (in the menu in Dolphin's main window)
3. Click Startup (group button/icon)
4. Select option "Folders, tabs, and window state from last time"
5. Close dolphin (Ctrl+Q or ALT+F4)
6. Start dolphin again

OBSERVED RESULT
After restart, dolphin opens the folder inside the button showing a “folder” icon.

EXPECTED RESULT
After restart dolphin should open all folders, tabs and windows opened from last time.
SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Kernel 6.1.29 (64-bit) / Linux Slackware 15.0+ / X11
(available in About System)
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.106.0
Qt Version: 5.15.9

ADDITIONAL INFORMATION