insurers tend to err on the side of caution when assessing if something is an additional risk . cynics would argue it gives them a loophole to increase premiums and escape liability. .A hard wired dashcam, if done properly, is no more of a risk to insurers than a plug-in installation. A tangle of wires and attempting to power several devices from one socket may be riskier.
Another riduclous situation was that many insurers regarded fitting winter tyres as a notifiable modification and some charged a premium. Despite winter tyres being safer in winter.
The association of British Insurers realised this is ridiculous and most , but not all , insurers have now agreed a commitment to allow winter tyres without needing to notify them as a modification.
Here is a list of insurers who allow winter tyres
https://www.abi.org.uk/globalassets/files/publications/public/motor/2019/abi-guide-to-winter-driving---the-motor-insurance-commitment.pdfA word of caution. The companies that allow it are sometimes individual underwriters. You may find that when renewing with your existing insurance 'broker' that they change your cover to a different underwriter. This happened to me. Fortunately the new underwriter was also on the list. My tyres are winter rated 4 seasons so I'm covered anyway but if your insurer is not on the winter tyre list it may be advisable to contact them to see if all seasons are notifiable as winter tyres.
Maybe ABI should consider similar schemes for things like hard wired satnavs.