After installing the security updates, WiFi only works once after a reboot, the moment you disable it, you have to either sludge forward with modem speeds on 2.4GHz-band or none at all if you are on 5GHz-band. Since these problems manifested after installing the security updates, it's slowly starting to point towards a driver/firmware issue instead of a hardware problem as some have speculated.
Some fixes for this are "phantom SIM", resetting WiFi settings or booting into safe mode. Only common thing with these "fixes" is the reboot; so far it is the only thing that will fix the WiFi but turn it off once and you're boned. Similar issues are noticeable with the WiFi AP: first try after boot works just fine, next one you have to try to force 2.4GHz-band on the AP along with 5GHz, causing the AP to "soft reboot". After this, you are very likely in need of a reboot as the AP will no show up.
After this breach of privacy and data security, along with the WiFi issues, I'm slowly starting to lean towards filing a complaint to either HMD or the local customer protection agency here.
Worst of all, the support forum topics I've checked somewhat regularly on have no official replies from HMD or Nokia, only second-hand information from people who have been in touch with support.