Earthian Weddings

There is no legal institute of marriage in Talitha Harbor. People are free to come and go in a relationship as they see fit without worrying about any legal involvement. With all of life's necessities provided, regardless of work status, there's no pressure to band together for survival. No one owns land or houses to be split or passed on to family. The society as a whole owns and shares everything. Resources are managed through their Vocational Government System.
Some people still like to give public proclamations of love. Traditionally it is a simple ceremony . The couple, or group if it's a larger union, will announce there love or union. For some it's a simple line, for others it may be a poem, speech, or song. When everything has been said they ask the crowd if they will witness the event, and the crowd will give their response. After there's an exchange of a small token or gift between the couple. When it's all done there may be a get-together of some sort to celebrate, but those vary widely.
Some Talithans want more than that. Though Earth is taught as a historically dark place they shouldn't strive for, the mysterious dead planet still holds it's intrigue. Information isn't held back in any way and Talithans have access to that history in a massive digital library.
Depending on the scale of the wedding, their plans may be met with criticism. Talithans are raised to be very careful about waste and preserve resources. Most Talithans respect this to some degree and some can be very diligent. A large wedding may cross the line for them.
The ceremonies are not illegal as long as the people holding them obtain anything used legally. They may have to save for a while, depending on what they're doing. But, they won't be stopped by any of the vocations.
There is one place in Talitha Harbor where they are not allowed, the island occupied by The Pure Dawn Collective. The small community takes preservation of the natural resources to a level that the rest of Talitha Harbor does not. They live in small huts, farm just enough to sustain themselves, and spend their free time without any form of technology as entertainment.
For the collective, there are no grand ceremonies celebrating unions. They will still have small ceremonies, but they don't include anything beyond the exchange of words and a small token. They also avoid anything that's distinctly Earthian, or from an old Earth culture. They fully embrace the idea of the old world being a dark place.

History

The Talithans are more than one thousand sol cycles or 1,175 Earth years removed from their ancestor's home planet. But, when the The Talitha Colony Ship left Earth it brought with it a vast database of information. It was a combination of many things, to include cultural ceremonies at the time. People from more than twenty different countries were included in the colony and the database focused the most on their history. But, it included others as well.
The voyage from Earth to Talitha Harbor took a long time, generation after generation was born and died on the Talitha. At first they held onto their customs, but over time they changed. Sometimes it was for practical reasons. As their journey became longer rationing became more important. As Earth died several colony ships had been sent out in various directions, and not all had a planned destination. The Talitha was one such ship, they had to hope they would find a habitable planet before the ship couldn't sustain them anymore.
They, of course, did find that planet. The Founders, which where the highest ranking crew of the ship, knew they needed to protect this planet and it's ability to sustain them at all costs. The Talitha was near the end of it's life. Part of that was creating a new culture and finding ways to make everything more sustainable.
Weddings had lost any legal significance before the Talitha had even landed. There wasn't any reason to change that. They had also broken down cisnormativity, couples and families of all shapes and sizes where the norm.
Early Talithan society didn't have any formal ceremonies. But, as time went on, and the Talithans spent more time reading about their ancestors, some wanted to bring these things back. Over time a Talithan ceremony to show long term devotion developed. As it did, the old ceremonies performed on Earth were mostly left to the annals of history.

Observance

Of course, not everyone was satisfied with the simple Talithan ceremony. They wanted something grander or with more ceremony to it. Weddings that use old Earth ceremonies can vary widely, like they did on the ancient planet. Some will stick with a single culture while others will combine several.
Some Talithans will trace their ancestry back to their Earthian counterparts. For everyone, it is a mixed bag. The original population had less than fifty members from each of the represented countries. But, strict record keeping has made finding where one came from easy for most. There are Talithans who will choose a favorite from the list bring back parts of that culture, to include wedding ceremonies.
Some wedding traditions are easier to mimic than others. They may not have diamond rings, but they still have jewelry. Their society is mostly secular, and there's no legal reasons to have an officiant. But a friend or relative can still play that role. Since there are no rules, a child could even fulfill that role.
Other things though, are difficult or not allowed. Intentionally breaking anything without a utilitarian purpose is highly frowned upon. There are community buildings, but they can't be rent for personal use. They are always open to everyone. Any indoor weddings could include random passerbys as well as invited guests, unless it's in someone's home.
Any traditions including animals would be a challenge unless it happens to include arthropods or sea life. The only Earth animals found on Talitha Harbor are rabbits, chickens, and quails. They are all heavily regulated and kept in small farms. There is an abundance of sea life and arthropods, but killing a creature for anything other than food or another purposeful resource use is highly taboo and illegal in some cases. Though, a ceremony in which there was a use for the animal after would be less frowned upon. I.e., they're going to eat it, or give the remains to a vocation that can use it.