Only useful arrows are Silver
Silver Sword does great damage , Frostner probably does a bit more (Crush > skeleton)
Silver dagger may actually be the best option though (not tested) since it allows faster movement, less stamina drain - and you'll proc Holy damage more often.
2 top tier HP foods and 1 top tier Stamina Food
Use Mead to top up your food bonuses

Ideally you don't want to get hit - so Tasty mead is 100% worth the HP regen trade-off

He has a very brief down time and you need to smack the donkey out of him during that time then run around dodging - repeat

EDIT : Did some research and - Frostner secondary attack is the best thing to use for damage - while spending as little time as possible in Yagluth's face

yeah I think the same .. I killed two times before this and I think the same, they made it a lot more diffcult. I think that it does a lot more damage. With a friend we already failed twice killing it, and we had to retreat to fight another day. Previously with bonemass, fire resistant potion, you could tank it and kill it in a breeze. Previously it was too easy, now it's too difficult.
(Also before it didn't had the lava/blast attack, this was added before H&H but also noticed that)

damn...I think that it even moves faster (that was his main weakness, being slow!)

I'm going to try with silver arrows tho, they make spirit/undead dmg, but they are pricey.

According to a web site I checkd that listed every creature and its weaknesses Yagluth does not have a weakness to piercing damage like the rest of the Prarie creatures. The site recommended Frostner or anything else with good blunt damage.

Silver arrows might workbut Yagluth doesn't seem to take more than normal damage from spirit based weapons. but he seems to be set up to be effectivly immune to arrows.

Site i'm referencing;
https://www.slythergames.com/2021/02/23/valheim-enemy-weaknesses-resistances/

best way to defeat yagluth now is with frostner or silver sword. Make a circle of small earth mounds wait for full health pop a mead and swing away at him. When he calls meteors run away and repeat. use the earth piles to hide behind incase he uses the lazer breath.