What about MemberPress ?

MemberPress is a WordPress plugin that allows you to create a members-only area of your website by gating content; it also handles the checkout process and lets you sell digital downloads.

Membership has a courses plugin that:

MemberPress Courses

• Full-featured WordPress LMS.
• Quick and easy activation.
• Profit-driven design, optimized for student success.
• Quizzes and student progress tracking.
• Resettable, expireable, and shareable certificates of completion.
• No complex coding.
• No fiddling with pages, sub-pages, and custom post types.

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