WANNA HELP?
You can do so by sending funds to charities if you can afford it (the littlest sums will make a difference!), by fostering or adopting a dog , but also by spreading the word about the issue!
There are lots of charities trying to make a difference, and I don't know all of them - please reach out if you notice that one is missing!

IN MAURITIUS
As far as I know, they don't have a hands-on volunteering program, they are pretty small charities where people are working very hard on emergencies and don't have time to organise things on a bigger scale. If you try and contact them, they might not always be the greatest at replying in my experience, but don't let that deter you from sending financial help if you can: if you follow their pages, you will quickly come to realise that they are hard at work and helping out a great deal.
Most of their work is dedicated to feeding the strays, picking up injured doggos from the streets and making sure they receive proper treatment, trying to find them families, fostering (most of dog-loving people there end up with 10-15 dogs at home on a regular basis - no joke!), finding funds to sterilise the strays... It's a never ending struggle.
Most of those work mostly on Facebook (if they have websites they are not always updated) so I'm linking to the FB pages.
All Life Matter Animal Sanctuary:
https://www.facebook.com/ALMMauritius/
Well being of the strays:
https://www.facebook.com/helpourstrays777/
M'Ile Pattes:
https://www.facebook.com/milepattesmaurice/
Second Chance Animal Rescue:
https://www.facebook.com/scarmauritius/
La Meute de Zion:
https://www.facebook.com/LMDZOfficial/
Paws Mauritius:
https://www.facebook.com/pawsmauritius/
Nou Toutou:
https://www.facebook.com/NouToutouMU/
Happy Tails Sanctuary :
https://www.facebook.com/happytailssanctuarymauritius/
Rescuer of Animals in Distress :

IN EUROPE
In the UK:
They raise funds for sterilisation programs in Mauritius, help financially several of the Mauritian charities in their daily tasks and bring some dogs to the UK to find them families. They are always looking for people to foster dogs.
Paws Care and Rescue UK:
https://www.facebook.com/careandrescuemauritiusintheuk/
https://paws-care-and-rescue-uk.co.uk
https://www.instagram.com/pawscareandrescueuk/
In France:
They help bring dogs from Mauritius to France to find them families. They too are in constant needs of foster families.
Association Aristo Pattes:
https://www.facebook.com/Association-AristoPattes-1624035354513643/
L'Arche d'Emy:
https://www.facebook.com/larchedemy/
In Germany:
Förderverein Strays of Mauritius e.V. :
https://www.facebook.com/Förderverein-Strays-of-Mauritius-eV-2098585903553417/

BECOME A FOSTER FAMILY
I've been a foster family for four dogs (including the one on the picture above!) now. My biggest fear was not being able to let them go, to be heart broken. In the end it's been a truly gratifying experience. Not only you get to be proud for actively contributing to saving a dog's life, but you also know that he or she will have a nice life and be loved.
A practical advice I remember reading, for those who are afraid they might not be able to let go, was to ask for a dog poorly suited for your daily life: for instance, take a huge dog if you live in a small flat, or one that sheds a lot if you're a bit of a cleaning freak :) This way, even if you are bound to be sad when then dog leaves, you are also somehow relieved!
And if you do end up falling in love with your foster dog, most charities will allow you to adopt him or her.
Another preconceived idea of mine was that fostering a dog could be quite a long term commitment. Some dogs do take a while to find their forever family, but in my experience, young small sized dogs find a family in 2-4 weeks only.
It really is a beautiful experience, one that I highly recommend (it can also come in handy if you are thinking of adopting a dog but aren't sure you are ready for it). If you have any question at all about it, please feel free to get in touch.

ADOPTING AN OLDER DOG / A STRAY DOG
The idea of adopting an older dog or a street dog is usually a bit scary. Will the dog get used to their new way of life? If they are scared of people, will they ever be able to trust them? Will they get used to living in a house, in a flat?
All stories are of course different. When it comes to mine, I adopted Alfred (pictured above - on the first day when he joined us, all skin and bones and injured, and one year later in London) straight from the street. I never knew exactly how old he was (the vets back then said he was between 4 and 8!) but one thing is certain: he was not young, and he has been living on his own either his whole life or for a long time. He was very scared of strangers and of children, but in spite of this, he proved very easy going: house trained after only a couple of accidents, quiet in the flat, he learned several tricks very easily, was well mannered, and oh so affectionate...
In comparison I often meet people who adopted a pure breed dog as a puppy, and whose dogs have behavioural issues. There is no rule!
The plus side of adopting an adult dog through a charity is that they know what the dog is like, there will be no surprises.
Adopting an older dog can also be scary as you know from the start that your time together is limited. From a cynical point of view, it can be a good thing when you know you can't commit to taking care of a dog long term. An older dog also doesn't need as much exercise and entertainment as a young one, which can be better suited to some lifestyles. No matter what, adopting an older dog is knowing that you are allowing them to experience love, sometimes for the first time in their life. I was heart broken when I lost Alfred, but I don't regret for one second taking him in.