With the new kernel installed, my desktop system boots quickly to the sddm splash and hangs for awhile, then after 1 minute the cursor appears, then after 2 more minutes the plasma desktop appears, and everything works as expected. I booted 2 times to verify this behavior and it is the same each time. This installation is on a SSD and normally boots very quickly to the plasma desktop.
I looked at ~.xsession-errors, but I don't see anything abnormal there (not that I would know what to look for ....).
System: Host: dibl-patience Kernel: 4.19.12-towo.1-siduction-amd64 x86_64 bits: 64 Desktop: KDE Plasma 5.14.3
Distro: siduction 18.3.0 Patience - kde - (201805132121)
Machine: Type: Desktop Mobo: ASUSTeK model: ROG STRIX X299-E GAMING v: Rev 1.xx serial: <filter> UEFI: American Megatrends
v: 1401 date: 05/21/2018
CPU: Topology: Quad Core model: Intel Core i7-7740X bits: 64 type: MT MCP L2 cache: 8192 KiB
Speed: 4111 MHz min/max: 800/4500 MHz Core speeds (MHz): 1: 4111 2: 3608 3: 2331 4: 4220 5: 4080 6: 4376 7: 4254
8: 1957
Graphics: Device-1: NVIDIA GP106 [GeForce GTX 1060 6GB] driver: nvidia v: 396.54
Display: x11 server: X.Org 1.20.3 driver: nvidia resolution: 1920x1200~60Hz, 1920x1080~60Hz
OpenGL: renderer: GeForce GTX 1060 6GB/PCIe/SSE2 v: 4.6.0 NVIDIA 396.54
Audio: Device-1: Intel 200 Series PCH HD Audio driver: snd_hda_intel
Device-2: NVIDIA GP106 High Definition Audio driver: snd_hda_intel
Device-3: Logitech HD Pro Webcam C920 type: USB driver: snd-usb-audio,uvcvideo
Sound Server: ALSA v: k4.19.12-towo.1-siduction-amd64
Network: Device-1: Intel Ethernet I219-V driver: e1000e
IF: enp0s31f6 state: up speed: 1000 Mbps duplex: full mac: <filter>
IF-ID-1: br0 state: up speed: N/A duplex: N/A mac: <filter>
Drives: Local Storage: total: 2.27 TiB used: 916.85 GiB (39.4%)
ID-1: /dev/sda vendor: Samsung model: SSD 860 EVO 500GB @ size: 465.76 GiB
ID-2: /dev/sdb vendor: Western Digital model: WD1003FZEX-00K3CA0 size: 931.51 GiB
ID-3: /dev/sdc vendor: Western Digital model: WD1003FZEX-00K3CA0 size: 931.51 GiB
Partition: ID-1: / size: 58.81 GiB used: 9.89 GiB (16.8%) fs: ext4 dev: /dev/sda2
ID-2: /home size: 393.18 GiB used: 51.34 GiB (13.1%) fs: ext4 dev: /dev/sda4
ID-3: swap-1 size: 5.00 GiB used: 0 KiB (0.0%) fs: swap dev: /dev/sda3
Sensors: System Temperatures: cpu: 40.0 C mobo: N/A gpu: nvidia temp: 37 C
Fan Speeds (RPM): cpu: 0 gpu: nvidia fan: 0%
Info: Processes: 246 Uptime: 11m Memory: 31.33 GiB used: 1.89 GiB (6.0%) Shell: bash inxi: 3.0.29
Edit: On an HP laptop with entirely different hardware, the problem is the same.
On a Dell laptop with LXQt desktop, the problem does not exist. So I conclude it is a problem with KDE/Plasma desktop only (I don't have a gnome or xfce desktop to test).
Edit #2:The problem is NOT the new kernel. Seeing the report of problems with systemd-240, I booted an earlier kernel, and the problem remains the same. So ... maybe I need to downgrade systemd and see if that is the problem.