The IR blasters can usually be flashed with open firmware like tasmota or esphome. I started with IR as well. The downside for me was that IR was one way. You can tell the unit to turn on, but you cant know if it actually did turn on.
I had something manual setup originally as well, but it became a bit of a maintenance hassle. Moving configs to devices was a bit of a pain, and generating keys wasnt easy.
Not the person you asked, but i have a mitsubishi electric heatpump, which i have hooked up to homeassistant via an esphome library. It has a header on the controller board that you can connect to.
Normally the header is for their $200 controller and app, i spent $10 on the parts.
An alternative (which doesnt fully meet your requirements for browser based) is Jetbrains Rider. You can use its remote development feature to have your code on your server, and the IDE on your local computer.
Another option to get code to and from your device would be to use git to commit and push your code. There are git apps for android that should work for this?
More exotic software will probably come from the internet, but the basics should be on the DVD. Good luck with your journey, reach out if you need any help, im sure everyone here would be happy to assist.
Try increasing RAM voltage? Might make it more stable under load. I had a similar issue, clean memtest, but games would randomly crash. Increasing RAM voltage fixed it.