We're looking at about fifty years after the Exodus. The Star League is barely a memory, and nobody in the ELH or even the returning ex-Clanners would even remember what the Star League was, except through the various (and varied) historical accounts.
It would take some time, even years for the ex-Clanners to hole up somewhere to do their research concerning the many SLDF regiments that remained behind, they will also have to be able to get over the prejudices that they were doubtless taught in Clan schools about the units that refused to follow A. Kerensky. All of these units eventually joined the Houses, who were reviled by the Clans as causing the downfall of their beloved Star League, although...they would also be exposed to countless historical documentaries that would show more than enough blame on all parties present at the time, including Kerensky. After the cleaning up the mess caused by initial heads exploding, anything could happen:
If Terra was so holy, the first stop would be Terra. Since subtlety was never a Clan trait, they could be less than cautious and broadcast their identity and intentions for everybody to hear. Then ComStar would welcome them with open arms and they'd never be heard from ever again.
If they took the Dark Caste route, they might successfully contact one or more ex-SLDF units and be shocked. These are not really SLDF members, they are another generation or two down the line, they are SLDF fanboys and cosplayers, with absolutely no interest in restoring the Star League because they know it isn't possible.
Sure, the Houses fight over succession but even the Houses know it's a joke -nobody has the strength to conquer ALL the competition.
They were told that there'd only be people living in caves when they returned, yet the IS is in recovery. The Star League may be looked upon as a golden age, but for the Houses, and worse, the Periphery nations, they were vile oppressors...what else did the Clans lie about? If they ran into ANY Dark Caste, they would realize they were lied to a lot...and exposure to the IS would be a major eye-opener.
Their problem would be, the massive amount of readily available information for them to sift through, before making a decision based on knowledge, which is why the Minnesota Tribe chose to continue on their way -they didn't like what they saw.