You do realize theres hundreds of instance admins? Theres no way for the dev to collaborate with each one. Youre better off looking to your favorite instances and donating to them directly.
This isnt the same as a humble bundle deal, where they have software licenses to sell and contracts with the publishers/devs.
I'm not sure how that would work with those being two separate sets of developers + instance admins. I don't even think you can do instance admins + Lemmy devs in one place.
Server admins, responsible for whatever instance you're browsing from and whatever instance the post is on (I use lemmy.dbzer0.com, you're on sh.itjust.works, these are two different admins/teams of admins)
App devs, in Sync's case ljdawson
Are you looking for a single donation to go to all of these groups?