> How do I transition from etags to treesitter? … to LSP: You don’t throw your tags away. If you run an LSP client it will add an “xref-backend” transparently,

> How do I transition from etags to treesitter? … to LSP: You don’t throw your tags away. If you run an LSP client it will add an “xref-backend” transparently, so Emacs will get all references and definitions from the LSP server. If you turn off LSP mode, Emacs will fall back to the etags backend. I don’t think you need any configuration for this to work. Treesitter modes do not implement an “xref-backend” AFAIK.