The insidious nature of Steam is the fact that they’re basically a PC gaming business monopoly,
Steam is a market leader, not a monopoly. Steam looks like a monopoly because it is the natural effect of being a market leader.
The fact that 80%+ of PC game sales are through Steam doesn’t seem to faze or disturb them, when it most definitely should
Reasonable disturbance but I personally will only categorize this as a concern.
If you aren’t sure, install with secure boot off. If you like adventure, install with secure boot on and see if secure boot causes problem or not. If yes, then install with secure boot off