If what you really want is to re-examine controversial or contrarian positions (i.e. restart old flame wars), many places will not be very keen.
If you really want a platform to be heard, start a blog with a comments section and learn to promote it.
If what you want is a venue to test your logic against others who are similarly motivated... join an IRL debating club.
If you want to learn from experts, try YouTube channels and then go where they engage with their support base e.g. pay them on Patreon. Expert subreddits are good too if you are willing to play by the rules.
If you just want to shoot the breeze about casual topics, Twitter is still there.
Comments
Depends what you mean by "have a discussion".
If what you really want is to re-examine controversial or contrarian positions (i.e. restart old flame wars), many places will not be very keen.
If you really want a platform to be heard, start a blog with a comments section and learn to promote it.
If what you want is a venue to test your logic against others who are similarly motivated... join an IRL debating club.
If you want to learn from experts, try YouTube channels and then go where they engage with their support base e.g. pay them on Patreon. Expert subreddits are good too if you are willing to play by the rules.
If you just want to shoot the breeze about casual topics, Twitter is still there.
(edit: formatting)