10.53.2 solved all my issues (no or very limited and lagged syncing on iPhone/iPad, by a day or so, zero new notes showing up on latter esp, delayed or no new note creation possible etc, nonfunctional Evernote on iPad for a week) except for two remaining issues.
Thanks you!
(And nb: browser version of Evernote on PC has always functioned robustly for me)
Remaining issues for me:
10.53.2, like 53.1, won't allow me to download any notes to my iPhone iPad (even a single note selected individually). I select a note for downloading and the downloading circle just hangs and the note never saves to device. There's maybe some sort of interface problem between the Evernote server and saving on a local device.
the button icon for download notes seems to malfunction now--it doesn't show notes that have already been downloaded (it remains greyed out for them), and as above, will hang if you select it (attempted download frozen, stuck in death spiral with nothing happening)