UK or Australia?

Scholarship opportunities are very rare in the UK, both in general and for international students. Usually international students in the UK are funded by their country's government or self funded.

Why are the scholarship opportunities so rare? Are the qualifications for scholarship programs solely based on grades and educational background? thanks!

Depends upon national citizenship, personal savings and planned level of uni study.
Within England there is very limited funding opportunities available to cover the tuition fees of overseas citizen undergrad students who are ineligible for student loans.
The competition amongst international applicants for tuition fee funding bursaries and scholarships to cover accomodation costs & living expenses is intense.
Most international students either receive financial support from their relatives, fund their uk uni studies via personal interest accruing loans from finance companies in their homeland or get it paid by the government of their nation of citizenship.

I'm not sure about student funding opportunities for international students in Australia.
But quite a few unis in the USA and Germany tend to have quite a few available for academically high achieving applicants who are fluent in at least 2 european languages including english.

Basically they just don't really exist. There are some bursary schemes for students from low income backgrounds, but these don't come close to covering the full cost of attendance. There are some tuition fee reductions and bursaries available to students with refugee status as well. But in general otherwise UK universities just don't have scholarships really in most cases.

Also just following from the above comment, I'd note that university in Germany is free at public universities for all students apart from a nominal fee each semester which is for the student union and a student travel card (about 100-200 EUR a semester usually), with the exception of one state in Germany which charges a fee of ~1500 EUR a semester for international students (I forget which one - Rheine something I think?).

You do need to pay your own living costs and may need to prove you have the funds to support your living costs while there, and will need to arrange private healthcare insurance or to go on the public health insurance programme there. But in general, fairly cheap by comparison. However many programmes are available only in German and require C1 German on matriculation (you can apply with B2 German but need to get to C1 by the time the course starts), although there are a number of degrees available in English language as well (mainly in business/STEM subjects).

Are German unis as strict when it comes to offers and admissions? thank again!

Depends on the course. Some have restricted numbers (I think they call this numerus clausus or something like that), but many are just open admission i.e. you just sign up and as long as you meet the matriculation requirements (which I believe usually include e.g. proof of language skills in German and/or English at the appropriate levels, proof of funds to cover your living costs while in Germany, proof of completing your high school studies etc) it's usually just automatic. Some programmes may require specific courses to have been covered in high school (e.g. classics type courses require the equivalent of the German Latinum/Graecum examinations).

Does that mean studying in the UK as an international student is quite hard?
Even if that's the case, is it still worth it to study there, opportunity wise?