For long-term, permanent notes, I'm using Obsidian with Nextcloud and FolderSync Pro (which I also use for backing up some Android stuff to my Nextcloud).
For quick, easy notes while on the go (or that I need quick access to while out and about), I use Memos, which is more of a Google Keep replacement.
I use Memos, but I didn't like the MoeMemos app when I tried it. Text to small and horrible theme. I installed a shortcut to the Web client and it works great. I usually want dedicated mobile apps for the stuff I use, but Memos is so simple, I don't think a mobile app is needed.