In the same stroke though the onus to supply backing to any given position or assertion is on the one claiming facts.

Valve supporting gaming on Linux is common knowledge here. For very niche knowledge or hard to google terms, I'd agree but there's a limit. One cannot expect to cite sources for every single bit of common knowledge.

This one is easily found out through a simple search and all but burden of proof isn’t on the one asking for proof

The amount of work required to ask for a source is similar to googling it directly, maybe asking is even more work because usually selecting the claim and then right-click --> "Search web for XYZ" works just fine.