I finally got the q-beta running on my fp 3+, so far everything seems to work, except for the known bugs (eg: no sound via bluetooth working).
I just tried everything at home yesterday - w-lan/wifi working perfect. But when I left today and wanted to switch to mobile-data, there was no internet connection. It appears, that no mobile data is used, although the phone says it is connected to 4G. I tried to reset the connection data (via reset options ) and reset the phone like mentioned here: [SOLVED] Wi-Fi broken after an update of pie-version - #9 by lorain
It seems that the phone/ e os (don’t know where exactly the mistake is) can not automatically get the APN-information through the SIM-card. I had to search for the information, which depend on the provider you have. Then I filled everything and now it works.