I'm still on Thunderbird 52 because the upgrade to 60 ruined my calendar. I hope the next ESR version works better. :-/ I don't even use Thunderbird for email

I'm still on Thunderbird 52 because the upgrade to 60 ruined my calendar. I hope the next ESR version works better. :-/ I don't even use Thunderbird for email anymore, so I guess what I really want is a standalone calendaring application that I can migrate to.