Not really, I mean one of main features of Initiation is access to the metaplanes and that's an early advancement for most awakened characters. "what to do in the metaplanes" should be in the first mag book imo.
This has been an issue for a few editions, as the metaplanes have been left mostly untouched since 3e.
(and depending on where you stand in the "Magicrun" argument, that is a good thing)
TBH, most of the reasons for "why" a mage would want to go to the metaplanes has been "retconned" in the past few editions as they made magic more friendly and easier to acquire (and some argue, turned SHADOWrun into MAGICrun..)
Historically these are the reasons a magic visited the metaplanes:
1: Learn a spell without paying karma:
Spells used to be harder to learn and cost a bit more karma each: Not to mention being locked to a learned force rating. Through a metaplanar journey, a mage could change the force of a known spell without having to relearn the spell, or learn a new spell at a given force rating. Also note that a metaplanar quest was the only way to learn spells above force 9 (I think?).
2: Learn a meta-magic technique. It used to take a trip to the metaplanes to learn how to do things like centering, quickening, and other meta-magics.
3: Reset their power points. Adepts who underwent a physical trip to the metaplanes could reset their power point abilities, and pick new ones. (basically a PP re-roll)
4: learn the True Name of a spirit for Binding/Ally/Destruction. Spirits (were) are next to impossible to completely destroy, even if "killed" on a metaplane. However, knowing the True Name of Spirit allowed you to control and even destroy the most power spirit relatively easily..... Hello Ares Firewatch teams and Bug Spirits.
5: Discount on Initiation. Initiations used to be more detailed, and came with more risks than they do now... One of the ways to offset the karma cost and risk (or, really, exchange the risk) was to go on a metaplanar quest...
6: To learn something. Spirits know a lot of shit about just about everything. The trick is to find the one spirit that knows that you want to know... And a meatplanar quest can achieve that... if it doesn't kill you.
As to what the metaplanes look like... well, they are different, lets just say that. There are couple of metaplanar write ups in 4e, a couple in 5e (I think), and a couple in 3e. Only thing that is clear, is that its not a reflection of our reality. (the plane of Ice in 4e, was written as the plane consisted of a giant snowflake crystal with all the spirits buzzing about it, and off in the distance was a the palace of the Ice Queen, the Spirit that ruled the plane... Street magic 4e)
