I'm attempting to wean myself off of Mac-specific technology, inspired by some impending hardware failures (see below), the not-falling cost of not-improving hardware, and the lack of budget growth.
Following a suggestion from Peter Williams, I'm using reveal.js based on Peter's template, which I have previously played with a little with mixed success. The slid.es editor seems nearly fully featured as a replacement for keynote, but I quickly dropped it because of its subscription-only paid features; the cost-benefit analysis is that Keynote is much cheaper than slid.es for someone like me, since Keynote cost 30 dollars one-time for ~10 years of use, while the minimum usable plan for slid.es is 10 dollars/month, or 1200 dollars over the same period. If that was the tradeoff I was considering, mac+keynote would be about the same as linux+slid.es, since I'd be paying a few thousand dollars for the mac.
I'm taking the somewhat ridiculous approach of raw HTML/CSS editing with the Chrome inspector as my interactive testing tool. This is a little tedious because of the html tagging, but that's honestly not so bad; it lets me do the hard work with the keyboard instead of the mouse. The biggest problem is the learning curve of css, but I look at that as skill and knowledge worth having. If you don't, this is probably not the approach for you. I hope, though, that some day there is a slid.es-like solution that is reasonably priced.
Another problem is image editing, which was pretty convenient in keynote, but there are plenty of other decent-to-good image editors out there, e.g., gimp, preview, etc. For cropping and opacity, which are most of what you want to do, css works and can even be tested interactively in the browser. But, this should also give more motivation to just make the figures presentation-ready in the code.
Anyway, the talks I've created are hosted at github, and they're fully-featured: you should be able to just click these links and walk through the talks.
My "Tracing the Flow" invited talk on High Mass Cluster Formation: https://keflavich.github.io/talks/HighMassClusterFormation_TracingTheFlow2018.html
Some slides for a work meeting on the ALMA-IMF project, with a technical bent: https://keflavich.github.io/talks/ALMA_IMF_W51_SgrB2.html
If you want the pdf version of either of these, add ?print_pdf to the end of the URL, then use your browser to print and save to pdf.
Some pictures of the impending failure. My mac doesn't close any more, and the charger cable has frayed severely:
