Brits or better prepared Italy could do that. But there is other changes too depend about exact POD.
Certainly the Oromo would kill any mass migration of westerns moving through there lands.
The Habesha weren't east to conquer, the reality is that you'd have to near exterminate them to have European settlement.
Even then the effect of toppling down one of the few internationally recognized African Monarchies would possibly send who ever tried to conquer Ethiopia in a very bad position as there are European powers already there working with the Ras.
Why were these groups harder to conquer than the various groups in Tanzania, Uganda or Kenya?
Tanzania, Uganda and Kenya are largely farming Bantu who never densely populated the forest zones, folks tend to forget that Africans aren't really a tropical people. They only recently moved into those regions and relied on Banana as their main form of subsistence.
Ethiopia was densely populated with a very different terrain and people, it creates a very different scenario than say South Africa or Angola.
Not true about Kenya and Tanzania. Most of those groups are Nilotic.
Are you talking about the farming groups, or the population as a whole?
In Kenya at least you have the Kikuyu, Kamba, and Luhya for Bantu, and Luo, Maasai, and Kalenjin as Nilotes. I think the edge numerically goes to Bantus but it should be noted that the Kikuyu population boomed tremendously in the first half of the 20th century.
The problem with this is the fact that by the time any European power took a real interest in Ethiopia, the country had already been more or less reunified after the Age of Princes and began modernization. Plus there's the fact of public opinion: Ethiopia's a Christian power, so the civilizing aspect is pretty much out (yeah I know Italy was Christian as well, but the Italians didn't really think their first attempt at conquest through, look at the lack of troop numbers and supplies). And there's the Russian support. I'm not sure when that actually started but it has to be taken into account.
As to the idea of Egypt tendering the Ethiopians up, its unlikely. Ethiopia is pretty far supply-wise to launch a land invasion, even from Sudan. Finally there's the fact that most colonial nations only initially wanted control over the coastal cities, not the inland territories. In all you'd need a much earlier interest in Ethiopia on the part of Europe. Maybe the 1868 British expedition turns Ethiopia into a client state with a permanent garrison (after all they controlled the capital and had Tewodros II's son and wife in custody)? Aside form that I can't think of another possibility.
Not true about Kenya and Tanzania. Most of those groups are Nilotic.