I'm replying a few years later but hope this helps somewhat.
There used to be a solution to this. The (now defunct) service
Email This could scrape text from any web page and send it to your email. Then, to read on Kobo, I used the
Read Email Later service which gives you an email address to attach to your Pocket account. Anything emailed to that address will turn up in Pocket on your Kobo. It worked perfectly for me back in 2021.
Unfortunately, "Email This" no longer exists and I don't know of any similar service. The only solution I've found is to copy the text from the website yourself and paste it into an email which you then send to your "Read Email Later" address.
If anyone knows of a more automated solution, I'd love to know. For now, it's a case of copying-and-pasting or (if it's a paid email newsletter) forwarding the newsletter to your Read Email Later address.