Is there a way to sort by level requirement?

Unsure about sort (maybe with some extension?) But you can search for giveaways of desired level[s].

https://www.steamgifts.com/giveaways/search?level_min=2&level_max=5

To search for giveaways level 2-5 for example.

For more information about parameters, https://www.steamgifts.com/discussion/1kgzB/new-search-parameters

This also is a table of different searches by level whitelist regions etc.

https://www.steamgifts.com/discussion/Ov1oC/hll-hot-links-by-level-copies-and-region-restricted-added-useful-search-tool

Thanks folks :)