I'll try to explain how I git where I am with this.

I used the same Google keep as you for multiple years, but Keep isn't available offline on PC, it's interface doesn't help in interlinking, and it is not open source. Last one hurts especially considering its a Google project, one of the decent ones at that, and thus it can always be cancelled next quarter.

I moved in to Emacs+org-mode on PC, and Orgzly/Orgro on Android. It syncs notes via syncthing, on my lan, no internet required, but can be used. This gives it a ruledundancy. Org-mode is also much Kore organic for note taking, since it allows collapsing trees, embedding code, equations. Adding links can be done inline, unlike Keep (I haven't used it in last year so that may have changed).

As for search, Keep is good enough if your notes only have shopping lists and one off stuff that you require every now and then. Keep is, however, terrible for organizing any amount of knowledge. Org-rifle, for eg. gives context aware search results across my entire notes folder. The power is unmatched by Keep, where notes are mostly siloes, and interface too verbose to let you a birds eye view.

And did I mention Keep takes multiple seconds to load on a good connection? And that its closed source? For some, that alone is reason enough.

Finally somebody makes some sense. I have an even lazier system, I type a search into bing like "bizidea - hydroponic urban farming" and save it to bookmarks and when search "bizidea" there are all the billion dollar ideas.