Investigation/research would be more on the source code auditing / internal fork / etc..etc.. / general effort to see if the application is secure enough to be used on a company environment. Vault warden could be easier to install or even consume less resources, but if bitwarden has enterprise support it would be hard to sell vaultwarden.
Another option that I'm looking for is psono, but I'm still building the helm chart for this guy.
I'm currently looking into Myki and KeeperMSP but neither are free for proper sharing for business teams.
I did see psono.com when I was looking at options which does have a free version.
Have you checked out https://psono.com/? Its open source, has browser extensions similar to lastpass and you can host it yourself. (Docker, ubuntu, centos, ... whatever you like)
Full disclosure: Im the main developer behind psono.