The informed opinion on the Subject is easy to obtain. Explain to the insurer that there is an intention for certain electrical goods to have a particular provenance and what that provenance is. If the insurer is given an accurate description, their reply to what this means to an Insurance Policy is the only informed opinion each individual will need, as I am sure each policy is unique to a particular residence, as location, and quoted values are not typical.
It is much more important that the individual who has seen the DIY options and finds them attractive has an improved understanding of all the risks. The usual disclaimer that the build is done at one's own risk and there is a risk of electric shock. Works very well when a DIY build is being considered as a pre-warning. For many, it is enough reading to be a deterrent to take the build on as a self-built endeavour. There is also what the post-build means, and post-build risk is very rarely discussed.
Keeping the information whole is what really matters.
Note: Insurance, as a business, has two methods of being a lucrative source of income. Of which one is receiving payment but not receiving claims? The other is investigating claims and discovering reasons that void a policy and not to make a claim payment.
As an individual fully signed up to the methods proposed to produce electrical goods used for audio, and also having been loaned a reasonable amount of audio items produced DIY produced by individuals. I fail to see how my sharing information is a dire warning.