Installed magisk after LineageOS upgrade and now wifi doesn't work

I have a OnePlus 7 Pro. I had LineageOS 17 (Android 10) with microG, magisk, and vanced on it running just fine for almost a year. I upgraded the Android version to 11 first (which LineageOS documentation says is a pre-requirement) then I upgraded to LineageOS 18, and everything seemed to work just fine. I can confirm that my recovery and wifi worked. A few days later I wanted to open Vanced YT, but it was no longer installed, then I noticed that magisk was no longer installed. So I installed it according to it's instructions which was basically using the app to patch the boot.img I got from the extracted files (from a payload-dumper) and then installed the produced magisk_patched-24200_Y0Qmv.img. Ever since then is my problem. I can no longer turn on my wifi, I no longer have recovery mode, and every time I turn on/reboot the device I am greeted with a "System UI Crashed" error message. I can hit ok and everything else seems to work as expected. With the exception to my wifi not being able to turn on What I've tried: - re-flashed the original boot.img - re-flashed the recovery image - uninstalled magisk - I tried re-flashing other images from the payload dump (modem.img, etc) the same way the LineageOS documentation said to upgrade and I get the following error

fastboot flash --slot=all modem modem.img
fastboot: error: Could not check if partition modem has slot all

I have no idea what that error means. Nothing changed. I'm still greeted with the same crash message. I still can't turn on my wifi. And I still can't boot into recovery mode. To make sure I'm clear, my question is; "Where should I go from here? What things can I tell you in order to help me get my wifi working again, and to fix this 'System UI Crashed' error message?"