The system at hand is off line and I’m mostly using command line, but I’ll try installing it on another system using pamac and copy the packages from /var/cache/pacman/pkg or some such.
Check out the man page for pamac, there are options to build from local directories. Depending on the kind of package you might need the base-devel meta package installed on the target machine to make this work.
Okay - solved - kinda Adapter is now up and running but doesn’t see the access point, will probably need a range extender or something similar.
Solution:
Found a driver for isl3886usb on AUR
installed it using pamac (as suggested by Hanzel) on a different machine with internet access .
copied the isl3886usb-firmware-someversionnumber-any.pkg.tar.zst from /var/cache/pacman/pkg/ to the other machine (via thumbdrive)
plugged in the USB wifi adapter
It probably just worked from that point on, but no connections were offered due to the accespoint being out of range … at least that is what I conclude from this for now:
$ hwinfo --netcard --wlan --bluetooth | grep -Ei “model:|driver:|status:|cmd:|file:|detected:” | grep -v “Config Status”
Model: “Qualcomm Atheros AR8152 v2.0 Fast Ethernet”
Driver: “atl1c”
Device File: enp7s0
Link detected: no
Driver Status: atl1c is active
Driver Activation Cmd: “modprobe atl1c”
Adapter is now up and running but doesn’t see the access point, will probably need a range extender or something similar.