Life starts when you plant a garden.

Are there any other traditions/techniques similar to the use of icaros from places outside of Amazonia? If so, what can we learn from them?

Songs and music are used the world over in ceremonial contexts. Think peyote songs, African drumming, Aboriginal song lines, Tuvan throat singing, monastic chanting, kirtan etc...

I'm on board 100%, I've been looking into permaculture solutions for a while now.

yup, brain fart

They don't call them icaros, but in North America the Indians also learn and use songs taught to them by the plants.

After drinking alone and with shamans, I will say - shamans certainly add something very tangible and distinct to the experience and add a much deeper level of work to the ceremony for me.

They are in no way necessary at all. Very helpful in every way, but not necessary. Kinda like when learning guitar - you dont need a teacher at all, but you can learn to play better faster if you have a good teacher, and the better the teacher, the more you will learn. Nothing is wrong with teaching yourself, and nothing is wrong with learning from the deep wisdom of someone more experienced.

For some people a shaman might be a bit more necessary - for example if you are trying to cure epilepsy I think it would be better to sit with someone who has lots of experiences safely guiding people because of the danger involved. I know of someone who cured his epilepsy with Ayahuasca BTW - a friend of mine.

If someone has cancer and might die in the next year I think they are better off visiting a shaman then going it alone - just because the shaman can take them deeper faster. They have a lot to lose, so maybe can benefit from someone who has decades of experience (the shamans I stayed with in Peru usually had over 30 years of experience as a curandero, which is a lot of knowledge!).

And in the Amazon at least, it isnt just about drinking Ayahuasca.... Many locals dont even drink it when they go to ceremony! There is also the dietas, secondary plant medicines, energy work, massage and bodywork like bone-setting, vapor treatments, flower baths, icaros ect.... I have seen some people heal without ever taking a sip - they just had the shaman work on them.

But if you are just trying to learn about the spirit world, experience Ayahuasca, or in search of healing for less dangerous problems, you are probably fine drinking alone if that is what you feel called to.

Having never experienced a ceremony with a shaman, I cannot accurately state that it is worthless or without benefit. But I can say that my first time with the drink I spent half of the time alone in the woods and half with a spiritually minded friend. I can say without a doubt that the time spent with him and the time spent alone had very different feelings to them. The CEVs and OEVs were more intense alone but the feeling of depth and spiritual connection was greatly amplified when he was with me and offering me his opinions while I rambled on and on about the many ideas and revelations I was having. I think this is the effect that the shaman may have. Like I said, I cannot make any definitive claims having never drank with a shaman before but that is my belief at this time. I can, however, say that when someone tells you that they think you "NEED" or "HAVE TO HAVE" a shaman that they are incorrect. Maybe some people need a shaman. And I think that those people probably know and already have their mind set on having a shaman. If you feel comfortable going into the experience without one then I don't think you need one. In the end the most important aspect of the experience is your attitude followed by the set and setting.

Another thing that a shaman usually brings to the table is chanting, drum beating, and other musical influences. I think we all know that music can have a profound impact on any altered state of consciousness. From the most abusive cocaine user to the most humble ayahuasca drinker, music can drastically enhance or even reduce any experience. I think that is another reason the experience is altered when a shaman is present.

I find that more often than not those that tell you that you NEED a shaman are those that have never experienced the medicine and are just saying what they have been told by a documentary or those that have religious beliefs tied to it. That, of course, isn't true for everyone but it seems to be largely the case. There are positives and negatives to both methods. You just have to find what is right for you and what will do you the most good.

I think you may be right, a lot of people, especially online, say things they've heard without actually having whatever experience they're talking about. If I would've listened to what people say, I may have never tried morning glories, as they get a lot of grief, yet I had magical experiences with them, that led me to ayahuasca and dmt.

I think that analogy is too simplistic.

I would not go hunting in Alaska without a guide. I could die out there without one.

People get lost and some of them die just hiking in the National Forest's of North America.

On a basketball court, I could only embarrass myself.

I just see a Shaman as a very experienced guide. Not everyone needs one, but some do.

Experienced is ambiguous, there is experience with the plants realm, and there is experience in conducting a session. There is experience in healing practice. If you find one that is experienced in all that at the same time, congratulations.
Just don't give credits too fast too soon when the holy word falls, because in the end they are only-human too.