The One Ring™ Strider™ Mode

You would need to have a good understanding of the core rules to use this.

Nope, it uses its own ruleset (The One Ring 2e)

The rules for playing without LM will work with any number of group members. So you can get together with friends and no need of one of you to be LM.
Then, there are also rules to make a starting character more competent from the get go to survive alone in the wilderness. Those will be need to be partially or totally removed if you have a group of 2 or more adventurers.

Playing co-op is even discussed at the start of the booklet:

"COOPERATIVE PLAY
This supplement is geared for solo play, but can
also be used for play with two or more players in
a small Company, without the aid of a Lore master.
When you are playing in a group without a
Lore master, the normal conversation you would
have with other players is expanded to include the
details of the world you inhabit. When a question
or situation arises which would normally be
resolved or depicted by the Lore master, the group
can collaborate to decide what happens, or use
tools such as the Telling Table (page 10) and Lore
Table (page 11) to help come up with an answer.
With cooperative play, it’s imperative that
players share the narrative spotlight, allowing
each participant to “take the lead” at times in envi-
sioning the world around the Player- heroes. Stray
from allowing one player to...See more become the de facto
Lore master, and take turns if necessary to foster a
collaborative experience."

This digital book is just Strider Mode, no Peoples of the Wilderland or Lifepaths included here.

There is not announcement of digital publishing of any of those booklets, but there was an unofficial confirmation that all 3 booklets will be printed as a part of some supplement on the future

Not really.

You CAN use 1e adventures with 2e by changing enemies stat block to 2e (this has been done by fans already) and then changing task difficulty (very easy) and NPC stats (very easy to do). But, Strider Mode leans heavily on 2e rules, so you need 2e core rules to bridge the gap.

This was the question I came here to get the answer for too! Having a hell of a time getting a group together, and this seems like a good way to practice too.

I am wondering this too. Do I need the full core rule book to play Strider Mode, or can I get by with just the Starter Set?

I posed this question over on BGG. The response that I got was that you need the Core Rules. The Starter Set is not enough.
https://boardgamegeek.com/thread/2877058/strider-mode-compatible-starter-set

On the Starter Set product page (here on DTRPG), someone responded this:

"Yes it is compatible, you can use all the Shire material there for playing solo"

¯_(ツ)_/¯ It would be nice if there were an official answer from Free League.

I went ahead and purchased Strider Mode just to find out whether I need to buy the Core Rules or not. At the top of page 3 it says "Strider Mode is supplementary to The One Ring — the core rules are required for solo play, and familiarity with those rules is assumed". Also, there are references to page numbers in the Core Rules throughout Strider Mode.

As an owner of all of the things you're asking about (Strider Mode, Core Rules, and Starter Kit), and as a solo player all the way back to buying the original VG Ambush and GMT's Thunderbolt/Apache Leader off the shelf of my FLGS, my opinion is that you will be able to create & play through an adventure in a solo mode using the Strider Rules and the Starter Kit. If you're smart enough to read and understand how to play the Starter Kit, you're smart enough to figure out how to use Strider mode with it for a one off adventure. It would be worth my $5, since that seems pretty cheap for a mechanically sound solo mode if you're already an owner of the Starter Kit.

Where it is going to fall over is the continuation of your character's longer-term story, as you attract the attention of The Enemy Hunt and rise up through the ranks of experience doing jobs for your Patrons. But I'll still maintain that if you look at the Revelation Episode table on pg 14 of Strider mode that you're smart enough to figure...See more out what to do with using that table to narratively put an obstacle in front of your character, whether you're using the mechanics directly from the Core Book or not...

So, yes of course the Core Rule book is going to provide you with a larger, ***far more interesting solo experience***. But frankly if you want to play a campaign of any kind in The One Ring settings, you'd be better off getting the Core Rules than the Starter Kit. The Starter Kit is mechanically how to play, the Core rules add in how to string those adventures together for the benefit (and detriment) of your character(s), whether we are talking about solo or group play.

My $3.56...

I replied on the Starter Set page here (DTRPG), I also posted an extended answer that I'm pasting here to be clear.

"Well, those are two different answers to two different questions:

1. Q. Is Starter Box enough to play Strider Mode?

1. A. No, you need more rules for a complete experience, especially character creation.

2. Q. Is Starter Box compatible with Strider Mode?

2. A. Totally compatible. In fact, if you want to play Strider Mode in the Shire I will say that is is required. Not because of the starter set of adventures, but because of the Shire sourcebook and map, they offer great material, descriptions, history and adventure hooks to play Strider Mode for a lot of time."

Yes

It won't work seamlessly with AiME, as the contents here are specifically tweaks to the new TOR 2e, but with a little houseruling you could use the tables (oracles) and perhaps tweak the journeying rules with what is in here. Bear in mind that all the tables use the TOR feat die, which is a d12 numbered 1-10 with special symbols on the 11 and 12. You can ofc use a standard d12, but I thought I'd mention it in case you pick it up and are surprised.

Hey, your set of houserules is super helpful as I'm starting my test playthrough, thanks so much for sharing!!!