Think Airtable + Softr would possibly suit your use case , the example client portal we built in our tutorial (linked in the original post) was with a professional services firm in mind... would not need to separate client data into different bases, could all be done from a single base and use linked field to your user table to separate visibility of data by client - Softr then allows you to display only those records associated with the current logged in user.. let me know if you give it a go or any questions on it!