With the introduction of the new inReach plans in September 2024, Garmin removed the ability to suspend a subscription.
It seems Garmin has come to conclusion that that was something customer didn't like, so they have changed their stance. It is now possible to suspend your inReach subscription again if you are in one of the new consumer plans (Enabled, Essential, Standard or Premium). You apparently can keep your subscription suspend for 12 months (consecutively), after which your subscription will be cancelled.
When you suspend, the change takes place at the end of your current billing cycle, so not instantaneous.
And of course you cannot use any inReach features with a suspended subscription, but that makes sense.