I am someone who has used pretty much all of the open source apps in this category before I found Obsidian. After a few weeks of use I paid for the license. I usually try to stick to open source but wanted to support the developers so this app keeps going. Between the app itself and the community of users and plugins I think there is nothing better. I’ve used things that have been open source and then abandoned and being open source doesn’t mean any software can be easily picked up by others and even if it can, many times the quality and responsiveness seem to suffer.
Having said that I would like to suggest to the devs that they make a commitment to the community: if the decide to stop developing/supporting this product that they will open source the code. I think that that commitment would make a lot of users who have expressed concerns here feel a lot more comfortable.
I had previously been using Joplin, Qownnotes and trillium. Joplin was very late to add plugins and they still are far behind this community. Qownnotes has a small but useful set of plugins and the developer is very active. trillium was built to be hacked and both the front end and backend are scriptable. Looked at logseq early but wasn’t ready.
I am happy with Obsidian and especially want to thank the community for the amazing plugins and themes.