BitWarden is open source, both server and clients. There's even a third party implementation of the server in rust that seems to be mostly compatible. Both the official and the third party server are self-hostable.
BitWarden runs their infrastructure on Azure, uses Azure managed databases and Azure managed backups. So I'm quite comfortable having my passwords there.
The only feature I miss is that I'd like BitWarden to send me an email with all my passwords, encrypted so that I own a backup of my data too in case the worst happens.