Scoped bolt action hunting rifles because they make great impromptu Sniper rifles. Also, as a resistance fighter in asymmetrical warfare you're not going to beat an army with firepower and continuous engagements. You have to rely on hit and run tactics and rack up a body count over time that will make the occupation too pricey to keep up.

A compact, takedown/folding stock version is also preferable because it will make it easier to carry it in a non conspicuous bag in the city and blend in with the population. Trying to hide in the woods against an enemy with thermal vision and surveillance drone capabilities is a bad idea. The only way to hide human activity nowadays is among other human activity.

Although lately shotguns did find a new use in the battlefield against drones. But once again, they're long, hard to conceal and you're better off hiding among population.

Also, speaking of new tech, I think it is worth learning how to operate drones. It might have become the safer way to do things like that. They're easy to conceal and easy to deploy and operate out of sight. As a bare minimum it will force the invader to use high power radio jammers that are absolutely not healthy to stand around over a long period of time, further increasing the cost of the occupation.