Yep, Felician, that is exactly it. Should be a straightforward patch. I'll do it, if noone beats me to it.

João

On Mon, Feb 13, 2023, 18:30 Felician Nemeth <felician.nemeth@gmail.com> wrote:
> - Following text appears in the minibuffer area: `[eglot] Server
>   reports (type=1): Unknown method textDocument/didSave`

Without actually looking into the details, this feels similar to an
earlier issue, which I unfortunately closed:
https://github.com/joaotavora/eglot/issues/360

The commit referenced in #360 only fixed the willSave part.  I guess the
solution to this bug report should be probably similar to that fix:
Eglot should check (eglot--server-capable :textDocumentSync :save)
before sending a textDocument/didSave.