Australia

We import all sorts of fringe political positions from the US.

I’ve seen it cited that the sovcit movement exists in 26 countries

We may have actually exported it to the rest of the world! In 1970, we had the Hutt River Province secede from the nation of Australia. To be fair to old Prince Leonard - he had valid grievances and was not just a nutter. The Australian Government was imposing wheat quotas on him when he was just about to harvest, and frankly didn't exactly offer him much in the way of services.

According to my 2-minutes of Wikipedia research (which makes me an expert on this topic, don't you know?), the Soverign Citizen Movement appeared in the USA in the "early 1970's". Which sounds to me like it may have drawn inspiration from the waves that Prince Leonard was making in Western Australia.

Tom Tanuki created a two-part summary of the two main Aussie SovCit movements:

p1: https://www.youtube.com/watch?v=ea_7jUU489g

p2: https://www.youtube.com/watch?v=IIrcWtuLkdA

A couple of interesting notes I remember:

• Being more closely tied to British monarchy, our versions seem to stem more from the Canadian variant than the US, but there's def plenty of crossover.
• Not sure if this is a big factor in the US movement too, but there's a big focus on the family courts, so plenty of them are disenfranchised divorced parents who lost custody and have engaged in collective harassment of ex-partners and legal workers like judges.
• One of the main SovCit movements comes from an indigenous liberation perspective. It's just as much a scam and stands in the way of actual resistance efforts, but there's more to it than just ultraliberalism (e.g. US Libertarian ideology) and contrasts with the US SovCit White supremacy tones you mentioned.

I think you most commonly encounter them in tax-related situations.

I know someone who works for the local government and issues notices for local taxes. In some ways it's a fairly natural progression to go from not wanting to pay your taxes to inventing some bonkers ideology explaining why you in fact do not need to pay taxes.

Comically, the city's first move with delinquents is to simply stop their refuse (garbage?) collection service.

There's a few in Perth. They occasionally paste some laughable text in the local papers proclaiming that they are sole bodies and not beholden to taxation. Or some other bumph. It's odd that all sovshitness seems to come down to not paying taxes, while still using all the facilities that taxation provides.