When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Also, a little more detail would be helpful. Where is this "Device Mirroring" notice appearing? Does it replace the "Projection" icon on the infotainment screen after you plug in the cord; does it appear as a full infotainment screen notification, or does it show up on your phone? A photo might help.
Why did you do a factory reset? Had it been working fine from when ever you purchased the car and all of a sudden this issue appeared and you did a factory reset for that purpose?
Since you say you are technical, we presume that you are using official Apple charging cords for troubleshooting since non-Apple cords have proven to be a problem with many of the C7 CarPlay issues?
Are you using the USB plug in the center armrest, or the one in the hidden compartment? Maybe try the other one.
Also, I’ve had mixed results with a wireless adapter. It worked about 50% of the time. Switched to a different wireless adapter, and now it works 100%.