(spoilers) I just found an easy way to fight armored lynels.
Eat attack up food (1.5x dmg)
Attach something blunt to a Royal claymore (moblin horn, lynel mace horn etc), and flurry rush an attack (2x dmg on flurry rush for royal weapons) . Armor melts in one flurry rush. (Any royal weapon works)
Use a royal guard claymore thats almost broken fused with a lynel horn. Does like 170dmg, and if you only hit him when mounted it uses no durability.
When his health is super low swap to a different weapon. Otherwise you might accidentally hit the ground and break the sword.
Best fuse items for weapons are from lynel drops... (55 attack from silver lynel)
Attach a octo balloon to several shields (save your rockets ;-) ) float up and using a Lynel 3x or 5x bow with a bomb flower (only uses 1 arrow and bomb but shoots 3 or 5 arrows/bombs) will eliminate all of their armour in one hit. You need to come close enough to ensure that all your arrows hit.
Then just beat them up as normal, flurry/mount etc.
Food also does help if you want to speed this up (3x attack up).
If you have a Lynel bow with not so good stats, rock octos will reroll the stats when they "repair". But the weapon does not have to be damaged, they will still reroll stats. Usually after 1 or 2 rerolls you will get a 5x (remember each rock octo will only do this once per blood moon).
unfortunately they are still like rockets. They expire after one use.
They are also slightly slower to rise and maybe (I never did the check) not quite as high, but they still do more than enough to get up high to do the damage.
Btw i have 3x attack up and a 3 shot 32 dmg lynel bow. Took me 5 bomb flowers to get armor off. But i was a bit far. Every time i get too close the bomb flowers kill me ....
Also, dazzlefruits on arrows. These confuse the Lynel and allow you to run up to it to mount and do that attack. Or Puffshrooms - since it loses sight of you. (These obviously don't remove the armour, but they are an easy way 'in').
The other thing is that if you are removing armour using melee weapons, then "hammers" work better than everything else. Attach boulders/rocks/spiked balls (talus hearts/construct dodads) to weapons as armour removal.
oh yeah, you do have to be careful of that. and you do need the arrows to hit. Move to where such a shot will spread hit the lynel (side on is a good starting point - like the lynel is a barn door!).
Also if you are not all fooded up etc and/or wearing the Fierce Deity set armour it will probably take two shots, but this is still a cheap investment for the lynels demise.
Also, honestly its been a while since I started so most of my bows are 5x 40 (or close to) because I kept rerolling them.
Also anyone interested, if you hit up a white or silver lynels, you can usually kill 2 of them with one bow. So you might lose a bow, but you will get 2 in return, netting you +1 new bow and a replacement for the lost one.
Find a Royal Guard Claymore and break it in the overworld. Then scour the Depths for a pristine Royal Guard Claymore (only certain areas are able to spawn one, like the depths under eventide - if a ghost doesn't carry the weapon you want, take it anyway and throw it away, this allows the weapon to respawn next bloodmoon). Savescum when approaching the ghosts to get a decent +damage mod on it. Fuse a Molduga Jaw on it and then use up all of the weapons durability except one hit, so the weapon will break next hit.
When fighting a Lynel, wear armor that gives you Bone Proficiency (if you don't have any, Kakariko Armor Shop sells some).
The resulting weapon can kill Lynels super quickly while on their back. Press the attack button very slowly to not accidentally jumpslash after the Lynel is dead.
Exactly, breaking a normal rusted weapon is prerequisite for it to spawn in the depths (aside from the traveller and soldier weapons, those always can spawn).
And yea, Attack up and Bone Proficiency can stack.