It would be a slack instance for people seeking tech jobs, so we could have channels like #backend-senior and #frontend-junior etc where you can discuss tips for interviewing, practice questions, etc.
Not totally clear what you're asking. Would the slack group be just for job seekers, or would it have hiring staff in there too? Would it be a separate slack server per company, or literally one server for everyone?
I was thinking one server and just for job seekers. Like a support group for people looking for tech jobs.
Maybe there could be channels per role/level, like #backend-senior, #ml-junior. So you could discuss hiring process and get tips from people looking for similar roles.
I know you've mentioned Slack multiple times, but please for the love of all things holy don't use a closed system that deletes messages and isn't easily discoverable via search engines. Zulip has built-in support for a providing SEO renders of the messages and I'd imagine one could easily self-host it in Oracle Cloud's free tier, or apply through their sponsorship program https://zulip.com/plans/#cloud-sponsorships