Case management. I use "cliniccases" which does most of the work but it is geared towards law clinics and does not have "billing". That can be improved but that's something.
What do you use for crm ? Is that self hosted too ?
There are softwares like cryptpad that solves collaborative editing problem for those used to google docs.
I use mailinabox for my emails and that has been quite great.
Libreoffice all the way. It has improved immensely. The import export to docx is becoming better and better.
I use a network shared drive to host all clients data, working papers and such. I have been thinking of " nextcloud" but I do not see the benefit.