And now to partially answer the original question, culled from the 200 or so people I follow, so I will have missed some I should have left in, and some of these might be of less interest to the HN crowd:

https://octodon.social/@craigmaloney - Linux, programmer, stuff

https://mastodon.social/@natecull - computery and other stuff

https://mastodon.social/@rysiek - security

https://mastodon.social/@Ronkjeffries - Well, it's Ron Jeffries

https://mastodon.technology/@Ronkjeffries - and again

https://mastodon.social/@andrewt - Maths stuff and odd observations

https://mathstodon.xyz/@virtuosew - Linguistics, odd observations

And then there are the maths people:

https://mathstodon.xyz/@peterrowlett

https://mathstodon.xyz/@Pecnut

https://mathstodon.xyz/@christianp

https://mathstodon.xyz/@icecolbeveridge

https://mathstodon.xyz/@mscroggs

https://mathstodon.xyz/@aperiodical

https://mathstodon.xyz/@j2kun

https://mathstodon.xyz/@csk

https://mathstodon.xyz/@neilbickford

https://mathstodon.xyz/@JordiGH