Hi, thank you for testing.
Actually browsing to:
http://myserver.local:22300/api/ping shows correctly:
{"status":"ok","message":"Joplin Server is running"}
while http://myserver.local:22300/api/sessions still shows:
{"error":"Not allowed: GET api/sessions"}

OK I tried with the windows app and the sync check worked.
I guess browsing to /api/sessions can only return ok when authenticating before (which is done within the app).

So Windows app ok.
Back to IOS: double checked credentials/URL:
Error: Please check that URL, username, password, etc. are correct and that the sync target is accessible. The reported error was: network request failed
Have to check on MacOS as well as it didn't work so far either.

Do Apple devices require SSL (any port) or SSL/443 when using joplin-server ?

PS: all this test is done locally on a private lan.