This one? https://dynalist.io/

Looks like it's still alive and kicking. I guess you're probably upset by a lack of updates or something - luckily upgrading to a paid plan would be a good way to incentivize whoever is developing it to continue working on it, at least at the margin.

I‘ve never been a customer, I‘m using Workflowy.

What you missed is that the paid offer didn‘t stop the developers to lose interest and… start Obsidian!

Long-term heavy Workflowy and later Dynalist user here. I am not upset that the developers started working on Obsidian instead, since I see Obsidian as the superior product, which has replaced both Workflowy and Dynalist for me.

Both Workflowy and Dynalist were treated as finished software for years. Workflowy did pick up again when it started losing customers.

Subscriptions do motivate ongoing development, but only if there's a threat to stop going or start incurring subscriber losses. Product software categories have different ratios of customers who buy subscriptions for the current utility vs the investment into future utility.