Hello there, Since update to 91 (91.1.1, Arch Linux), the flag "read only" on CalDav calendars is reset on Thunderbird startup. This is observed on all (two different) CalDav servers, on all of their CalDav calendars. None of my accounts are Google calendars. Reading this forum with people telling that "the way to add calendars changed", I obliged and re-subscribed to all my calendars, tried multiple times, restarting Thunderbird between every try. Auto-discovery works perfectly, finds all my calendars, but simply does not make the read only flag stick. A few of my calendars really are read only, so Thunderbird continuously pokes me about old events that it cannot dismiss (see https://support.mozilla.org/en-US/questions/1348450), which is frustrating. Especially given that the issue centers around a simple local-side flag not sticking between restarts...