I’m using a reMarkable Linux tablet and it’s been awesome. There’s a bunch of apps ported to it if you’re okay with using an older software release, and they give you full root access. Not FOSS or open hardware like Pine64 but really good experience and does not feel too limited.
You can kinda get autofill via a program called rofi-rbw on Wayland desktops (using wtype), but I found at least on Hyprland it often misses the field or the start of the password. I’d like to see a more consistent solution but definitely not via the official Electron app…