We have been working a lot on the speed issues as well. In general una is quick and doesn’t generate any warning when google is checking it for mobile compatibility.
like you we have discovered How much showcase and gallery views can delay loading. So we have reduced. The number of entries in the showcase we have on our front page. Q: is it possible to make lazy loading of the items not shown?
we also use CDN (cloudflare) and caches the entire homepage permanently, which makes is very fast for first time visitors as well. we also removed the call to google ads in the header.
optimising images and resizing them to the proper size gives a lot too