I tried chatting on some of the recommended apps on Reddit and I can confirm that none of them work.
Which bring me to the following question: How do you find people who are interested in long-term relationships online?
Note: Please don’t suggest looking in the real life.
In my experience, this is rare. Most people who meet others online started as friends with some common interest. I met my wife like this. It was never with the intention of a long term relationship, we were just friends online. We knew each other as friends for 2 years before getting together.
I would recommend DnD (or other games) as others have suggested too.
Also this is kind of random and I have no idea if it is a good idea, but maybe try https://duolicious.app/ - I saw it randomly the other day and your post reminded me of it.