My problem is that mask + effort steams up my glasses.
I ran into this problem ages ago, Martin, whenever I used a neoprene mask for cross-country skiing at temps around -15 to -20. That was an innocent age, it seems, and a niche- market problem. (How many bespectacled X-country skiers go skiing when it's 20 below?) Same problem arose but to a lesser degree when I used a slightly elasticized cotton/poly neck muff.
In other circumstances, I used to use a bandana under my face shield on my motorcycle helmet in dusty/hot conditions. Not a lot of effort, but plenty of heat, e.g. in the high deserts of the western U.S. Some fogging, but manageable.
My suggestion for cycling: (i) Use a bandana, that's reasonably tight across your nose, but looser across your mouth and chin; and (ii) use anti-fog treatment on your glasses. Bausch and Lomb make a kit for lenses.
Now it starts to get really bothersome: Does it make any sense to wear goggles over your glasses? I mention this only because Bausch & Lomb's package shows a downhill skier.
There's another issue, too: a cyclist friend here tried riding with a mask about six weeks ago. He found that his mask reduced his air intake by about a third.
Hope that's helpful, tho' I'm doubtful...