I'm using EteSync paired with Task.org.
I have this set up on phone, and my (Linux) computers. EteSync costs $2/month but it is well worth it. I also use it to sync Calendar and Contacts. There was also a flatpak version that lets you sync Memos in the same setup, but I didn't set that up. I wanted to stay with the .deb version. That requires a separate Memo/Notes sync, but I never bothered. One of these days I might.