There are many ways to add a gallery to an Oxygen website because there are dozens of plugins that provide gallery functionality. You could use any of them. However, in the spirit of keeping things simple, you might want to use galleries that are already built into the WordPress and/or Oxygen platforms.
So, you could achieve a gallery easily and with no, or at least minimal use, of additional WordPress plugins.
If you're planning on building a page with a gallery in Gutenberg then the default WordPress Gallery block is probably the easiest option. Please note that the WordPress Gallery block is not directly available in Oxygen itself.
No - it isn't. If you go to the Oxygen dashboard and look at the WordPress Widget elements available - you will see one called Gallery. However this is the WordPress Gallery sidebar widget, not the block.
The WordPress Gallery sidebar widget is a poor substitute for the WordPress Gallery block and I do not think it is (at the time of writing anyway) worth using. The results are not great.
In the video below I tried to use the WordPress Gallery Element in Oxygen, because I thought it would give the same results as its WordPress Gallery block equivalent. But I was mistaken.
The WordPress Gallery block is very easy to use and I think the results look clean, simple and excellent. The only downsides are that