yes they are quite similar, i even tried obsidiam for a couple of weeks on another phone, IMO "Lobseq" turned out to be easier to learn how to use. maybe you couldn't find their app because you have to download it directly from their official website, and then everything has to be installed locally, either on your computer or your phone!! their app is not on Google PlayStore, nor on F-droid.
https://logseq.com/
yes they are quite similar, i even tried obsidiam for a couple of weeks on another phone, IMO "Lobseq" turned out to be easier to learn how to use. maybe you couldn't find their app because you have to download it directly from their official website, and then everything has to be installed locally, either on your computer or your phone!! their app is not on Google PlayStore, nor on F-droid.