Fuck Substack. Just blog.
~~forcing students into surveillance situations should be illegal.~~ (edit: that's not a comment on your practice or actions, I'm sorry, in retrospect, it wasn't meant like that, I'm sure your intentions are nothing but good)
these are alternatives - some of them challenge students to learn a bit of underlaying technology like html and ssh-ing to a linux server:
https://neocities.org
https://tildeverse.org
https://smol.pub
https://codeberg.page/
@Daojoan titles of some selected blog posts by me:
Start of a new weblog
New software
Other blogging software, again
New Blogging Software
New year, new software