So after connecting through the IRC gateway, Slack now advertises this message:

Hello! We have news to share — we've decided it's time to close down the IRC and XMPP gateways to Slack. After years of evolving, Slack is at the point where the gateways can no longer handle all of our features or security needs. If you've been using the gateways for accessibility reasons, we're glad to let you know that it's now possible to navigate Slack by keyboard and with a screen reader — and we're making more improvements on a continual basis. Still, we know this is a disruptive change, and we want to help with this transition in any way we can. Please follow this link to learn more about the upcoming changes:

The two remaining solutions I found are, are irccloud, and if you are using weechat, you are also in luck, because there is a plugin called wee-slack. They both utilize the Slack API, so they are unaffected by the changes.