Using Logseq[1][2] for years and quite happy with it, especially since it has apps for tablets/iPad and phones as well, while being completely FOSS.
I am less concerned about open source than open standard. I have had my notes in text, jpg for more than a decade. Have used plain text editors (textmate?), nvALT etc and now use obsidian. I am sure these text files can stay for another 10 years even if obsidian itself goes out of business.