The markdown to presentation approach is great. You can manage your slide (or slips) as code giving you history, offline collaboration, pull requests, etc. I don't think you can do that with most other presentation tools. I've used Marp [1] for traditional slides, and wrote a GitHub template repo that outputs the Marp HTML to GitHub Pages [2]. Similar workflows should be possible for Slipshow.
[1] https://marp.app/
[2] https://github.com/ralexander-phi/marp-to-pages