Have you checked fsearch? https://github.com/cboxdoerfer/fsearch It got very good in the last 1-2 years and while ext4 fs don't support a file index like NTFS does, fsearch is still very fast, caches its results, offers similar features etc.
Now that ntfs3 has landed in the kernel 6, I wonder if locate/updatedb could leverage this file index? (I do plan a full-ntfs3 Arch or Linux install soon to experiment with such weird ideas :)
