Eglot, Ada Language Server, and Ada mode from ELPA with the following config:

    (use-package ada-mode)
    (add-hook 'ada-mode-hook #'lsp! 'append)
    (setq-default ada-xref-backend 'eglot)
    (setq-default ada-diagnostics-backend 'eglot)
    (add-hook 'ada-mode-hook (lambda () (set (make-local-variable 'comment-start) "--  ")))

    (custom-set-variables
     '(ada-fill-comment-prefix #("--  " 0 2 (syntax-table (11))))
     '(wisi-size-threshold 2))

Then for each project I have a .dir-locals.el similar to the following:

    ((ada-mode . ((eglot-workspace-configuration . (:ada
                                                    (:projectFile "AAA.gpr")))
                  (tab-width . 3)
                  (fill-column . 119)
                  (indent-tabs-mode . nil))))