I can’t offer much in the way of experience - but I have at least wanted to replace Amazon wishlist functionality. I’ve never gotten around to making the jump, so I can’t really say that I personally recommend any of these.
But when I was looking around, these are 3 options that seemed promising at surface level:
I’d be curious to know how it goes, so I hope at some point you update the thread with what works for you.
Another note: any time there’s a piece of software that you like, but don’t want to use it (because it’s proprietary, missing features, or whatever reason), alternativeto.net is an incredibly useful resource.
Here’s their list of apps with a wishlist feature: https://alternativeto.net/feature/wishlist/
Usually a great starting point.