I liked your suggestions but are they not obvious like in airgapped wallets you dedicate the device to either its wallet or a computer for wallet purposes and do not use it for personal uses. While in your suggestions you said, we should avoid SD cards to connect them to another device and should not scan QR codes from the hardware wallet (which are air-gapped). Don't you think using an SD card for other purposes while it should be dedicated to your air-gapped device will make your device not an air-gapped one?

This means your air-gapped device is not air-gapped if connected with the outside world, directly or indirectly. Never connect it to the outside world using an SD card, QR codes, or data cables, dedicate the whole setup for wallet activities and never open or update this wallet frequently, and talk about the updated files that you receive from the company, only prefer that company that has open source software like electrum or any other. Then you can also verify the authenticity of that update released by the company.