advice on pbn niche

I have a new website and I'd like to make use of 3 old websites of mine not in use anymore. They're all at least 5 years old and have DA30+. I want to turn them into the start of my pbn. However they're not niche related to my money website in anyway. All the content has been removed off them for about 6 months now. Should I add content that matched their old niches or add content that matches my money websites niche? Or a mix? What are your thoughts?

Write about your old niche and then just include the keyword in a article with a link to your money site. It looks a bit stupid if you have a website called "Armysupplies" and writing about undies.

Add new niche related content and let them age before you link out from them.

No one really seems to know so I've decided I'm just going to do both niches. I can make it work if its a personal blog. This way I'm splitting the risk/gains