That's not a Rust issue (not having a prompt to update LSPs). Lapce[1] is also a Rust editor, and it didn't keep downloading JS or stuff without a prompt. You can do what VSCode does, have extensions that ask for update, then update on change (even if using binary is the only solution, which I also doubt). Or if the issue is running LSP, ask if you trust a project folder on project start.

[1]https://github.com/lapce/lapce