I had a remarkable 2 for a year and was very dissatisfied with how hard it was to modify or run custom scripts or third party gui apps on it. Then came the subscription stuff and I ditched it.
Bought pinenote and even though I'm no linux developer, I've set it up and it works very well. Been using it for 3+ years now.
The build feels cheaper compared to remarkable, but the hardware spec is much better. And the best part is I can just run syncthing or kdeconnect or any linux desktop app on it and it's great.
My arch linux with KDE only uses 500Mb ram after boot and I have a handfull of apps in the autostart. So I would guess with some explicitly lighter desktop environment you can be well below 100Mb
If you have a chance to add an ssd or nvme you could allocate a decently sized swap partition and let the OS handle the rest.
Maybe you won't be able to watch full HD youtube in big fat chrome browser, but otherwise it should work just fine I think.