Where does the Community stand in relation to using LINQ, now in 2020? Re-reading old posts, there were problems using LINQ in iOS and also performance problems because of allocations made by the Linq implementation in old Mono versions that Unity was using. The general consensus was either "never use LINQ" or "avoid using LINQ, especially in big loops". Did this change?
I've been using linq for years now. Sure, be aware of any garbage that could be created. But personally I've never really had any major memory issues with it as long as I avoided doing it in things like every Update.
Based on vicarious experience, I think the implementation of foreach in the old mono created garbage every step of every iteration. I'm pretty sure that was fixed with the switch to the new .net implementation a few years ago. Using LINQ is still subject to creating garbage where a careful use or arrays may not. However, it's much quicker to work with, so I suggest using LINQ and saving the performance tuning once the profiler shows your queries are causing a problem.