I’ve been looking for 4 - 5 posts on how to synchronize my e calendar on my android smartphone with a third-party application and I can’t find it.
On my android, in account manager, I add the murena account but it only syncs email OR it doesn’t work: I switch to manual config and enter the IMAP config and nothing!
that won´t work for calendar as IMAP-protocol is for email only, you might use CalDAV-protocol for sync of calendar
Are you talking [murena online calendar → /e/OS-phone]?
in that case the /e/OS-account manager can do the same as DAVx5: system settings → accounts manager → add account → add WebDAV → enter credentials etc.
(edit after doublecheck: outdated info corrected)
Then go: calendar → calendar settings → config available calendars
if you´re talking [murena online calendar → some other android] go for DAVx5 as already mentioned by @make-nz