edie, I suspect your problem may be connected to the one in this
In mint update, can you go to Edit then Preferences and put a tick in the level 5 Visible box, click Apply, then click Refresh on the toolbar. Hopefully you should get about 5 updates some of which are for the linux kernel to 18.104.22.168-generic. Select them all and apply, when it's finished close everything and reboot then retry your wireless.
NB. If you don't get any updates listed for level 5, you may need to enable some of the other repos in Software sources such as Upstream, Imports and Backports.