[akvadrako]

I have been exclusively using a .so domain for about 10 years and never experienced any of these issues.

What specific network blocks it?

[jitl]

You can see a bunch of users reporting this issue in the link the user above posted: https://www.reddit.com/r/Notion/comments/f6x9mk/why_the_so_d...

[akvadrako]

I don't see any mentions of who's actually blocking it, just some guys work and a VPN provider.

There isn't any indication the blocking is worse than most other TLDs.