Mixed

When total training volume is equated, increasing resistance training frequency per muscle group (from 1 to 3+ days/week) does not significantly or meaningfully increase muscle hypertrophy.

If you want to maximize muscle growth, focus on getting your total weekly sets in. How you split those sets across the week (1 day vs. 3 days) does not matter for hypertrophy, provided the total volume is the same. You can train each muscle group once a week or multiple times a week; choose the schedule that allows you to recover well and stick to your program.