How do you actually manage client onboarding as a solo freelancer?

Every "client management" tool I've tried is either built for agencies with a team, or it's just a CRM with freelancer branding slapped on. I've ended up cobbling together Notion + a shared folder + way too many follow-up emails.

Curious what's actually working for people here — a real system, or still duct tape? And if duct tape, what's the piece that breaks first (intake forms, invoicing, scope creep, keeping track of who owes what)?