You don’t to do anything custom, just install the requirements. Running Supervised on a Pi is unsupported, it doesn’t matter what you do to try and install custom.
Good, just ignore it. It will still run as intended, you just lose “official” support from the Dev team if you have an issue. I have had a Pi3 running as a backup to my main machine for the longest time, no issues with updates etc.
The “unsupported” message has nothing to do with HA/Pi freezing. It’s more likely a database problem, or an issue with your SD card.
Follow this guide for a start to finish on setting up a Pi3/4. As mentioned, I’ve been running this way on a Pi3 for a long time, and recently purchased a Pi4 4gb, and have installed this same method using an SSD as the boot drive. No downtime yet after about 10 days.