With update to new KDE programs, especially dolphin 21.08.1 the navigation in dolphin gets very bad.
Dolphin starts fast.
Klick on subdirectory will always wait about 8 seconds.
Same problem in file selection dialog with Kate or Gwenview.
During waiting time no higher CPU load and RAM use, RAM is not exhausted.

No other program has problems, only KDE programs.
Firefox, bash commands etc. are all ok, have no problems with noauto entries.

STEPS TO REPRODUCE
1. Add noauto entries in /etc/fstab (without mounting)

I have commented out all not necessary entries in /etc/fstab except / and /home and rebooted system.
Problem was away, dolphin was then fast as ever.
Then added entries back one by one.
These both enties made than the performance problem:
>LABEL=EXT_HD6           /srv/nfs/m/h6     ext4           noauto,users,noatime,nodev,nosuid,noexec                         0 0
>LABEL=EXT_HD7           /srv/nfs/m/h7     btrfs          noauto,users,noatime,nodev,nosuid,noexec,compress=lzo,subvol=@   0 0

Just editing fstab makes performance bad, no change in mounts or other things.
I had a lot of noauto entries in fstab.
These cited two entries made about 1 second delay in every navigation step.
Together with more noauto entries the delay was about 8 seconds.


SOFTWARE/OS VERSIONS
Windows: Kernel: 5.10.68-1-MANJARO x86_64 bits
Linux/KDE Plasma: 5.22.5
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 
Qt Version: 5.15.2

ADDITIONAL INFORMATION
Discussion on Manjaro forum:
https://forum.manjaro.org/t/kde-dolphin-is-very-slow-at-directory-navigation-after-last-update-to-21-08-1/84975