There are already 3rd party Slack clients ( https://github.com/wee-slack/wee-slack https://github.com/wee-slack/wee-slack https://github.com/bkanber/Slackadaisi

There are already 3rd party Slack clients ( https://github.com/wee-slack/wee-slack https://github.com/wee-slack/wee-slack https://github.com/bkanber/Slackadaisical https://github.com/bkanber/Slackadaisical https://github.com/evanyeung/terminal-slack https://github.com/evanyeung/terminal-slack ). Using the same approach as them would let you have more control. OTOH, like someone else said, please contribute to improving riot/matrix instead.