A recent discussion seems to indicate that you can use sticky ads on mobile but that the UX may be degraded with multiple instances.

See that discussion here: [webmasterworld.com...]

Adsense offers "Anchor ads" as part of auto ads. These ad units are "sticky" and appear at the top or bottom of the screen on mobile. I believe that they are mobile only. Otherwise AdSense does not allow sticky ads except for large publishers. But there is nothing preventing you from displaying sticky ads from another ad-network.

I was using a plugin to insert a sticky ad via adsense and I noticed that it simply stopped displaying.

Imo this is an indication that Adsense doesn't want it and I won't use it again.