Managed to defeat a Jotunn in solo mode. They seem to have about 40,000 HP in that mode, so not as tough as in MP
The best tactic seems to be gates, at least early on. If you can get three gates built, your village can pretty much survive one night unscathed without you as the helthings won’t be able to tear them down and still do much damage in the time available. That leaves you free to go concentrate on the Jotunn for a couple of days game time. This means throwing most of the souls you get early in at the tinker so you can level them up to get stone blocks and iron bars. I did L3 tinker and L2 blacksmith to at least get a better sword. I think this might work pretty well in MP too.
It’s also really helpful,if there’s a shrine in the Jotunn’s path, helps you get back into the fight quicker when you die - as you pretty much inevitably will.
It was still touch and go - the Jotunn got to my village and has just smashed through the gate when I took it out but it got done.