Pinephone GUIs have a big problem communicating with the modem and anything that exists in that chip, this is why I circumvent the GUI and do the job directly with AT commands or the through the DBus with qdbus, I reckon you can disable the lockscreen by modyfing configuration files in ~/.config/ like with the suspend time
for Plasma have a look at the file "kscreenlockerrc", edit it and reboot
for Plasma have a look at the file "kscreenlockerrc", edit it and reboot