For hand writing i suggest using Rnote and for normal keyboard writing I suggest Joplin. Keep it synced using cloud provider or using Syncthing for free.
About organizational structure in Rnote I unfortunatelly recommend just saving files in a structure of folders. Rnote is the most polished alternative to hand-writing capabilities of OneNote I’ve found :c
About importing notes. I don’t think that’s possible but you can surely export them all to PDF from OneNote. I did that when I migrated.
I switched from OneNote a couple of years ago.
For hand writing i suggest using Rnote and for normal keyboard writing I suggest Joplin. Keep it synced using cloud provider or using Syncthing for free.
About organizational structure in Rnote I unfortunatelly recommend just saving files in a structure of folders. Rnote is the most polished alternative to hand-writing capabilities of OneNote I’ve found :c
About importing notes. I don’t think that’s possible but you can surely export them all to PDF from OneNote. I did that when I migrated.