Sometimes you have to pay for keeping things free, if that makes any sense.
FOSS can't exist in a vacuum. The developers spend a lot of time on things and they need to be paid for their efforts, otherwise we won't get great products like Sync.
If you want things that are well maintained and supported, then there has to be income for those owners to provide those services.
Sync for lemmy is a top tier client. I'm willing to pay to get and support that model. It's not like the 17 dollars a year is a big deal. I spend more than that on a single sushi roll sometimes.
Microsoft has been contributing a ton to FOSS the last 5 or 6 years.
Their flagship programming language, .net, is fully OSS and runs best on Linux.