Linux drivers and Windows drivers are two different animals. The experience of the last couple of years show us unfortunately that Realtek is not as committed towards the Linux community as it is towards the Windows side. The quality of their drivers is fluctuating.
That said, personally I think wifi has no business on a htpc devices, unless you are only watching low-res video or music only. I don't think you purched a N3150 PC for watching low-res videos. A cabled network connection is preferable at all times.
BTW, 'the latest LE8 "Extended" community build' is not a version number we use. We rather like real version numbers, and names of people that do those builds 
The community build is from escalade; best to post in his support thread to see if there's a driver bump available.
Thanx for the explanation. I thought it's a common problem. And I thought the community build uses the same drivers as the Libreelec source.
@ Klojum: I am friend of Wifi I've used a FireTV before my HTPC and I could stream 1080p flawlessly. But I understand what you mean.
I would be happy, if there might be a fix for Libreelec, as the problem seems to be a driver issue and not a bad wireless connection in my home.
Most of the time, I don't see any wlan networks in the LibreElec settings, to which I could connect.
I have posted in the thread from escalade, but I think I am the only one, who has wifi issues, as no one replies 
My knowledge about Linux (under the hood of Libreelec) is really limited and I have no idea, how I could install a different Realtek driver or how to fix the connection problems.
Maybe could someone please give me hint?
I really like the build from escalade, everything runs stable, but without internet and a stablish connection to my NAS, KODI is almost worthless for me.
My build is based on the libreelec-8.0 branch, the most significant difference except my added packages is upgraded kernel, mesa and sdl2. I ship the same drivers as vanilla LE, you can verify this by booting the latest beta and check if your wireless card comes up (I would think not). The RTL8723AE is supported by the kernel as far as I can tell, but there can be issues with SDIO, firmware, etc. In my experience Realtek = crap hardware and worse drivers.
I think the solution is here: GitHub - lwfinger/rtl8723au: Repo for RTL8723AU code before Linux Kernel commit
But I can't get it installed when I use Putty and try to clone, I get the error git not found, but the adress is correct.
When I copy the files to my local Userdata directory, and type make: sh make: not found 
