Caster can maintain concentration spell while in the ethereal plane as long as they caster doesn't violate any requirements of the spell.  (Line of sight, range, etc.)

Is this the Power of King Crimson?

One moves through the Ethereal Plane as one would move on the Material Plane. However, due to the mistynature of the protomatter of the plane itself, a traveler canmove up and down just as easily as along solid surfaces. - Manual of Planes page54

I don't know for sure but it's a plane between planes and you have visual and earing og normal plane, seems to mi that you can because of this. You are not disconected from normal plane and distances, visual or earing have not to be a problem to mantain spells but no to interact in any way with anithing of normal plane

It's not concentration. Which is nice.

So if I understand this correctly, this isn't like a smite spell or anything where the first time you transport to the Ethereal Plane and back the spell ends, but it lasts for the entire minute with the possibility of going to the Ethereal Plane and back multiple times?

Quote from Rolen_Mystic >>

So if I understand this correctly, this isn't like a smite spell or anything where the first time you transport to the Ethereal Plane and back the spell ends, but it lasts for the entire minute with the possibility of going to the Ethereal Plane and back multiple times?

 That is correct, hence the phrasing of "Roll a d20 at the end of each of your turns for the duration of the spell."

As long as you get the correct rolls, for the next minute: you will get an additional 10ft of movement on your turn, you get full access to your turn as usual (excluding the action required to cast the spell), and teleport to another plane which makes it impossible for others to affect you. Unless they are specifically able to do so. But unless you are facing an enemy that has powers within the Ethereal plane specifically, that wont matter much. Especially at level 5.

Just a quick question: Let's say you cast blink. While in the ethereal plane, you go through an ethereal curtain. When the spell ends, would you return on the plane you originally cast the spell on or the plane that the crossing led to (e.g. feywild)?

I haven’t read about the Ethereal Plane lately, but, if memory serves, this spell takes you to the Border Ethereal, where Ethereal Curtains aren’t a thing.

Love this spell. “For one minute, you have a 50% chance of becoming invisible, intangible, and indestructible any time it’s not your turn. You also gain an extra 10 feet of movement at these times.”

Is there gravity in the Ethereal Plane? If you're near some raging rapids in the Material plane and cast Blink, are the currents still a danger to you in the Ethereal Plane?

"the spell fails and the casting is wasted if you were already on that plane"

Can't be used to escape from the Ethereal Plane if you are trapped there.

Quote from RebeccaTheWizzard >>

Is there gravity in the Ethereal Plane? If you're near some raging rapids in the Material plane and cast Blink, are the currents still a danger to you in the Ethereal Plane?

Gravity, tangibility, and physics in general, rarely apply on the ethereal plane.

It is possible that a powerful enough rapid might have a spark of elemental force that extends into the border ethereal...but it’s just as likely that it doesn’t.

The spell is ruled in a way that makes it hard to move while ethereal. You become ethereal at the end of your turn, and re-enter the material plane at the start of your next turn. This means you are never ethereal during a time you can move. The only way you can move from your current spot while ethereal is if something on the ethereal plane moves you before the start of your next turn, which is difficult, as most naturally ethereal creatures suffer from low strength scores.

However, if you do want to use this to pahse through things, remember You return to an unoccupied space of your choice that you can see within 10 feet of the space you vanished from. Which means so long as you can see (i.e. through a window or something) a space, you can teleport to there.

Overall, the ruling of the spell makes it work really nicely as a protection spell, which is how it was intended, allowing you a 50% chance to blink away from danger before reappearing. And for those new to the spell, don't forget the 10 ft. teleportation before you reappear! Use it to avoid readied melee attacks by patient monsters waiting for you to reappear.

(note: the sorcerer in a game I DM rolls insanely for this, and has a habit of becoming ethereal every turn. Is their go-to defensive spell).

Casting word is:

Disapearium Volitus

Can you use "blink" to get out of being restrained???

Quote from Malcomfair >>

Can you use "blink" to get out of being restrained???

 I'd say no, cause if you were able to do so, then i would subsequently rule that you drop any weapons, armor, or anything else on your person. 

Quote from ZeggVonTheodrakugard >>

Quote from Malcomfair >>

Can you use "blink" to get out of being restrained???

 I'd say no, cause if you were able to do so, then i would subsequently rule that you drop any weapons, armor, or anything else on your person. 

Why would you rule that? It doesn't make any sense, and also it's much easier to just rule that you can't perform the somatic component when restrained

Quote from trapbuilder2 >>

Quote from ZeggVonTheodrakugard >>

Quote from Malcomfair >>

Can you use "blink" to get out of being restrained???

 I'd say no, cause if you were able to do so, then i would subsequently rule that you drop any weapons, armor, or anything else on your person. 

Why would you rule that? It doesn't make any sense, and also it's much easier to just rule that you can't perform the somatic component when restrained

How would you rule a sorcerer using this subtly to escape the restraints? 

Quote from Tyvos >>

Quote from trapbuilder2 >>

Quote from ZeggVonTheodrakugard >>

Quote from Malcomfair >>

Can you use "blink" to get out of being restrained???

 I'd say no, cause if you were able to do so, then i would subsequently rule that you drop any weapons, armor, or anything else on your person. 

Why would you rule that? It doesn't make any sense, and also it's much easier to just rule that you can't perform the somatic component when restrained

How would you rule a sorcerer using this subtly to escape the restraints? 

 That they succeed in the same way they would if they cast Misty Step instead