Yes, but the issue is they all share the same inbox, and my email server doesn't support server-side incoming filters so I can distribute mails to separate inbo

Yes, but the issue is they all share the same inbox, and my email server doesn't support server-side incoming filters so I can distribute mails to separate inbox folders that would be monitored by DeltaChat. Alias is a standard email feature. If Delta Chat want's to be usable as a general mail client, aliases should just work.