I would agree, probably not the right patch (Just provided it as it's what we do to make it work, just carrying the patch internally)

@nagifep aye, I did that to our own local servers (at the time I opened the ticket), working fine so far with the change. Apologies for not providing a update earlier.

I tested against a cyrus imap service we had, and it was showing no calendars. (Working with radicale, failing on Cyrus)

Tested this out against radicale, and now working as expected without the patch I mentioned in the ticket.

Was probing this further, and noticed in listFolders the following responses:
(with discover modified to use $response = $this->request('/', 'PROPFIND', $body, ['Depth' => 1, 'Prefer' => 'return-minimal']); - removed $roots[$component])