I’m eligible for the US Lifeline program to get a phone number for free. I would use it on websites that require a phone number, like Discord, which doesn’t accept numbers on services like Google Voice, and replace my personal phone number with it wherever necessary. And I would start using my personal phone number only with friends and family. I would NOT be using a provided lifeline phone, but rather a sim on my iPhone.
Throwaway number is the way to go but in some countries it is tied to your ID so it won’t help. And many people (usually those that were using Discord for a long time before diving into privacy) have important contacts there that they very unfortunately can’t move anywhere else.
In the US (OP’s post was somewhat US-specific), I haven’t had trouble paying cash for prepaid sim cards. Those services tend to be on the expensive side, but I suppose you don’t have to keep the number active after your Discord signup.
I would have suggested silent.link , while you can get a number not tied to your identity via esim, the main focus of numbers is a receiver for text and calls(also because it avoid people creating spam phone calls/txt). Which was originally for 2fa that only had cell # as an option. Also a number requires the user to be vigilant in paying their annual for it or they can lose the number. Also I think they can only cater for users in US, Canada and maybe UK.
Not everyone has an esim supported phone though