The failing test is ‘eglot-test-auto-detect-running-server’. I
can’t reproduce it here by running the individual test in a loop
(well it didn’t fail during 5 hours of looping). However it has
failed 10 times in the last 62 runs of ‘make check’. It only
happens on the 32bit ARM test machine but happens across all
tested configurations there.

I was able to run ‘make check’ a dozen times without failure using
the patch below. Let’s see how it does for a week or two of builds.

  --- a/test/lisp/progmodes/eglot-tests.el
  +++ b/test/lisp/progmodes/eglot-tests.el
  @@ -326,7 +326,7 @@ eglot-tests--auto-detect-running-server-1
          ("anotherproject" . (("cena.c" . "bla"))))
        (with-current-buffer
            (eglot--find-file-noselect "project/coiso.c")
  -       (should (setq server (eglot--tests-connect)))
  +       (should (setq server (eglot--tests-connect 20)))
          (should (eglot-current-server)))
        (with-current-buffer
            (eglot--find-file-noselect "project/merdix.c")